Chemical engineering education

http://cee.che.ufl.edu/ ( Journal Site )
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Title:
Chemical engineering education
Alternate Title:
CEE
Abbreviated Title:
Chem. eng. educ.
Physical Description:
v. : ill. ; 22-28 cm.
Language:
English
Creator:
American Society for Engineering Education -- Chemical Engineering Division
Publisher:
Chemical Engineering Division, American Society for Engineering Education
Place of Publication:
Storrs, Conn
Publication Date:
Frequency:
quarterly[1962-]
annual[ former 1960-1961]
quarterly
regular

Subjects

Subjects / Keywords:
Chemical engineering -- Study and teaching -- Periodicals   ( lcsh )
Genre:
periodical   ( marcgt )
serial   ( sobekcm )

Notes

Citation/Reference:
Chemical abstracts
Additional Physical Form:
Also issued online.
Dates or Sequential Designation:
1960-June 1964 ; v. 1, no. 1 (Oct. 1965)-
Numbering Peculiarities:
Publication suspended briefly: issue designated v. 1, no. 4 (June 1966) published Nov. 1967.
General Note:
Title from cover.
General Note:
Place of publication varies: Rochester, N.Y., 1965-1967; Gainesville, Fla., 1968-

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Source Institution:
University of Florida
Rights Management:
All applicable rights reserved by the source institution and holding location.
Resource Identifier:
oclc - 01151209
lccn - 70013732
issn - 0009-2479
Classification:
lcc - TP165 .C18
ddc - 660/.2/071
System ID:
AA00000383:00070

Full Text
































.... .. .....









TRANSPORTATION'S

FUTURE,


AN ENGINEERING

CHALLENGE.


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Chemical Engineering Education


VOLUME XV


NUMBER 2


SPRING 1981


68 Awad J.ela-,e
A Few Fundamental Concepts and
Applications of Cryogenic Heat
Transfer, Klaus D. Timmerhaus

54 The Educator
Eli Ruckenstein of S.U.N.Y.-Buffalo,
Dennis C. Prieve, Dady B. Dadyburjor

62 Departments of Chemical Engineering
ChE at Rolla, G. K. Patterson

78 Curriculum
Computer-Based Instruction: Is There a
Future in ChE Education?
Mordechai Shachem, Michael B. Cutlip

Classroom
86 Usage of Multiple-Choice Examinations in
Chemical Engineering,
Jude T. Sommerfeld

92 A Course in Special Functions and
Applications, Thomas Z. Fahidy

74 Features
Transport Phenomena in the Delaware,
Stuart W. Churchill

59 Conferences

59, 97 Book Reviews

60 In Memorium

96 Division Activites


CHEMICAL ENGINEERING EDUCATION is published quarterly by Chemical
Engineering Division, American Society for Engineering Education. The publication
is edited at the Chemical Engineering Department, University of Florida. Second-class
postage is paid at Gainesville, Florida, and at DeLeon Springs, Florida. Correspondence
regarding editorial matter, circulation and changes of address should be addressed
to the Editor at Gainesville, Florida 32611. Advertising rates and information are
available from the advertising representatives. Plates and other advertising material
may be sent directly to the printer: E. O. Painter Printing Co., P. O. Box 877,
DeLeon Springs, Florida 32028. Subscription rate U.S., Canada, and Mexico is $15 per
year, $10 per year mailed to members of AIChE and of the ChE Division of ASEE.
Bulk subscription rates to ChE faculty on request. Write for prices on individual
back copies. Copyright 1981 Chemical Engineering Division of American Society
for Engineering Education. The statements and opinions expressed in this periodical
are those of the writers and not necessarily those of the ChE Division of the ASEE
which body assumes no responsibility for them. Defective copies replaced if notified
within 120 days.
The International Organization for Standardization has assigned the code US ISSN
0009-2479 for the identification of this periodical.


SPRING 1981









educator


CiC Rachkendeien

Researcher and Educator


Compiled by
DENNIS C. PRIEVE
Carnegie-Mellon University
Pittsburgh, PA 15213
DADY B. DADYBURJOR
Rensselaer Polytechnic Institute
Troy, NY 12181

In 1977 Eli Ruckenstein received the Alpha Chi
Sigma award presented by the AIChE. The award
cited him for his "outstanding and prolific re-
search contributions in transport phenomena,
catalysis, colloid systems and thermodynamics."
Yet, up to 1969, Eli's work had concerned more
conventional aspects of heat and mass transfer
(such as distillation and fluidization) and inter-
facial phenomena. His early publications, includ-
ing a patent related to ammonia synthesis, were
largely in journals of his native Romania or of
the Soviet Union and, therefore, almost unknown
in the West. However, in a span of only eight
years following his arrival in the U.S., this man
developed enough visibility, in areas of research
previously unknown to him, to be accorded this
national recognition.
How can a man, then 45, faced with the
difficulties of adapting to a new culture, find the
motivation and time to successfully undergo such
a metamorphosis in research? Below are three
vignettes which may suggest an answer. First is

"When I was 12 I discovered Gogol
and Dostoievsky and not much later, Tolstoi
and Gorki. My adolescence was strongly
influenced by these writers and I
could hardly wait to return home
each day to continue reading."

Copyright ChE Division, ASEE, 1981


a biography of his life in Romania, as recalled by
several of his former graduate students and re-
written in a first-person style which attempts to
convey some of his personality. Then follow de-
scriptions of the atmosphere surrounding Eli at
Delaware and, later, at Buffalo, as told by two of
his associates.
"I was born in Botosani, a small city located
in the hilly area of Moldavie between the Car-
pathian Mountains and the river Pruth, not too far
from the border with the Soviet Union. The city
was an agricultural center populated with many
boieri (landowners). The numerous paysans who
farmed the land for them lived in humble shacks,
huddled together in small villages outside of the
city. Botosani itself was divided into two sections:
one containing the magnificent homes of the
boieri while the other was a slum, populated
largely by Jews. While the novels of Gogol and
Turgheniev provide an image of the opulence of
the boieri, the writings of Shalom Aleihem de-
scribe the misery of the luft menchen living in
these slums.
"My father was relatively prosperous when I


CHEMICAL ENGINEERING EDUCATION


C)EL!









was born, but our financial situation deteriorated
and became desperate during the great depression
of 1930. Few memories from my childhood de-
serve to be mentioned. I refused to learn the
alphabet until my teacher read a few chapters
from Cuore by Edmondo d'Amicis and a few
chapters from Robinson Crusoe. From that
moment on my fascination with books has only in-
creased.
"Our education at the lyceum was based largely
on the French tradition; yet I was attracted to
the Russian novelists. When I was 12 I discovered
Gogol and Dostoievsky and not much later, Tolstoi
and Gorki. My adolescence was strongly influenced
by these writers and I could hardly wait to return
home each day to continue reading. I am not a
loner but my fascination with Lermontov, Pushkin
and Dostoievsky transformed a child into an
adolescent, perhaps too early.
"I never visited Russia. The only message from
that country was the cold wind, Crivatul, which
came from the Russian Steppes each winter. But
to me, this wind was bringing the warm humani-
tarianism described by Russian novelists. I am
disappointed by the modern Russian literature.
The policy of the Communist Party has destroyed
a great cultural tradition.
"When I was fourteen the war started and
racial laws eliminated me from the state schools.
The Jewish community organized a private school
and very few of our instructors were professional
teachers. They were intellectuals who had lost
their jobs because of the racial laws, but they had
unusual enthusiasm, dedication, and that strength
of character built by difficulties. One of them,
Miron Grunberg, was only a few years older, but
he had an unusually broad culture and intelligence.
He was a model for all of us. Because of forced
labor, he died while still young. I was glad to
learn, two years ago, that his volume of poetry
has been recently published in Israel by his mother.
Having achieved this goal, she died a few days
after its publication.
"At seventeen I was drawn into forced labor
and worked on the construction of buildings by
carrying bricks onto a scaffold. Despite the long
hours, I stubbornly prepared for exams for the
11th and 12th grades and although I was out of
school, managed not to fall behind in my studies.
The Red Army liberated Botosani from the
Fascist occupation in April, 1944. Later that year
I moved to Bucharest, hoping to be accepted at
the University.


"I had no idea what to expect at the University
or even what career to pursue. Having grown up
in a small town, I felt completely lost when I first
arrived in the metropolis of Bucharest. Following
the advice of a family friend, I finally decided to
compete for a place in chemical engineering at the
Polytechnic Institute.
"Life as a student was a constant struggle. In-
flation soared: my father's monthly salary was
but enough to buy a bus ticket home. Hunger, cold
and humiliation were not strangers to me.
"There were also happy occasions. In 1946 I
met Velina Rothstein and we became close friends.
Together we read Spinoza and Nietzsche. Even
now I marvel at the unusual culture of this girl,
then 16. We were married in 1948. No one has in-
fluenced my life more than Velina.
"The Chairman of the Department of Chemical
Engineering at the Polytechnic Institute was
Emilian Bratu, one of the most admirable men I
ever met. After five years of study and my gradua-
tion in 1949, he chose me to be his assistant and
provided me with the best possible conditions,

"In 1946 I met Velina Rothstein ...
Together we read Spinoza and Nietzche.
Even now I marvel at the unusual culture
of this girl, then 16. We were married
in 1948. No one has influenced
my life more than Velina."

under the circumstances, for research. As an
assistant professor, I aided Bratu in recitation and
laboratory sections of his courses.
"By tradition, there were no formal graduate
courses offered by the Institute. The library had
very few of the books that were available to gradu-
ate students in the West and received journals
only after a year or more of delay. So Industrial
and Engineering Chemistry became my graduate
school, my textbook, and my teacher. I read each
volume in series, some from cover to cover,
beginning with Vol. I. Although there are some
advantages to this procedure, it is most inefficient
and is not to be recommended. It is like trying to
deduce the plot of a novel by starting in the
middle. Without knowledge of earlier develop-
ments, I began to understand the papers only
through stubbornness and repetition.
"In addition to a qualifying examination and a
dissertation, a major requirement for the Ph.D.
degree was to pass a test on Marxism and Lenin-
ism. Some of my colleagues spent more than a year


SPRING 1981









studying for this exam. I chose not to take it. In
1966 the law was changed to eliminate this re-
quirement and then, at the urging of Velina, I
submitted some of my papers as a dissertation and
received the Ph.D. degree.
"In Romania, as in most communist countries,
financial support for research is given to a small
group, chosen more or less arbitrarily by the Party.
Usually, assistant and associate professors work
for the department chairman, who then becomes
well known because his name is routinely added


Ruckenstein (left) and his colleague Stroeve.

to any publication submitted from the department.
Some of these chairmen are distinguished
scientists and deserve recognition; many others
acquired their position more through Party mem-
bership than scientific competence.
"Professor Bratu, who is now retired, was
unusually fair and modest in this respect. He pro-
vided academic freedom and refused to sign his
name as an author on a paper when he felt he had
not contributed enough. With the passage of time
my respect for him continues to grow as I better
appreciate how much I benefitted from the un-
usual atmosphere he provided.
"Understandably, papers published in Ro-
manian, or even Russian, journals are largely un-
known here. Until late 1950, we were not allowed
to send manuscripts to the West. When the ban
was finally lifted, manuscripts were returned due
to "lack of space." During the McCarthy era
scientists paid twice for living under a communist
regime.
"In the atmosphere of scientific exchange
which followed President Nixon's goodwill trip to
Romania in August, 1969, I was allowed to come
to this country as a senior NSF scientist at


Clarkson College. Velina accompanied me but our
two teenage children, Andrei and Lelia, stayed
in Romania with Velina's parents. I spent a most
interesting year at Clarkson, interacting with the
faculty.
"From 1970 to 1973 I was at the University
of Delaware. In retrospect, I perceive this to have
been a period of change in my research direction.
Published accounts of scientific research are much
more readily available in the U.S. than in Romania.
I became overwhelmed by the amount of informa-
tion available and the desire to digest all of it.
With this new knowledge came new questions,
which I then tried to answer and in the congenial
atmosphere at Delaware I had many enriching dis-
cussions with my colleagues. Gradually my re-
search shifted from heat and mass transfer to
catalysis and colloids, but only with the benefit of
time does this change appear as a discontinuity.
"At that time I was too preoccupied with the
frustrations of trying to get our children out of
Romania to notice the change. It was a very
difficult period for Velina and me. We shall never
forget the moral and material support we received
from Art Metzner and others at Delaware. Finally,
after two years of persistent effort and a lot of
luck, my family was once again together, this time
in the U.S."
***
This is how Eli might tell the story of his life
in Romania. Since his immigration to the U.S.,
he has held resident faculty positions at the Uni-
versity of Delaware and, later, at the State Uni-
versity of New York at Buffalo. Eli has served as
principal advisor for twenty-three doctoral and
post-doctoral students. Fifteen of his former
students from Romania or the U.S. now hold
academic positions and three are department
chairmen.
One of his former students is Dennis Prieve,
who is now on the faculty of Carnegie-Mellon
University. Dennis provided us with this next
vignette, which describes the atmosphere sur-
rounding Eli at Delaware.
***
"In the fall of 1970, when I began my gradu-
ate studies at the University of Delaware, I, like
many of my fellow students, found Professor
Ruckenstein awesome. Never had we encountered
anyone who so effervesced with ideas, who had
such deep knowledge of so many areas, or who
could readily identify and explain the essence of


CHEMICAL ENGINEERING EDUCATION











Ruckenstein's approach to engineering
science is like the impressionist's approach to
painting; the goal is to capture the essence of an
object or a phenomenon without producing
an exact image or description.

complex phenomena so clearly and succinctly. We
soon discovered he was also a warm person who
enjoyed sharing his knowledge and ideas with
others, especially students. Word spread that the
best way to do a literature search on any thesis
topic was to pay a visit to Ruckenstein's office. His
encyclopedic knowledge of the literature on most
any subject of interest to chemical engineers and
his nearly photographic recall of important papers
became legendary.
"While detailed knowledge of what has been
done in a given area is impressive in itself, it is
the creative use of that knowledge in a continuous
proliferation of ideas which is Ruckenstein's forte
and the most powerful source of inspiration to
students. In those days at Delaware, one of the
hurdles graduate students encountered on the way
to a Ph.D. was the "original proposition." We
were asked to find an original research problem,
not related to our M.S. or Ph.D. research, and
defend an approach for solving it. We soon learned
that the second part-the solution-was easy com-
pared to the first. Months were sometimes spent in
the quest; meanwhile ideas acquired value like
precious jewels. Once again we discovered that a
discussion with Ruckenstein could save months of
searching.
"Ruckenstein's vigor, enthusiasm and deter-
mination in research are contagious to those
around him. When I began working with Rucken-
stein on my Ph.D. research (he rejected the notion
that any graduate student worked for him), I ex-
perienced the true excitement of research. At the
same time I became astonished by his youthful
energy and unbridled drive.
"My topic was the influence of colloidal forces
on the transport of hydrosols. Several times per
day he visited my office to discuss this work or
some new paper he had just read. He often said
how pleased he would be if I would awaken him
in the middle of the night with news of some
breakthrough. Even now he telephones me long-
distance to discuss his, or my, research. This
almost continuous interchange of ideas provides
an electric atmosphere in which, for example, he
and I produced twelve publications.


"My experience was not unique. Berne Pulver-
macher (now with DuPont of Switzerland), a
classmate of mine, did his Ph.D. research on the
aging of supported metal catalysts by sintering.
This work opened what has become Ruckenstein's
second new research area: catalysis. Rakesh Jain,
another classmate (who is now a faculty colleague
at Carnegie-Mellon University), submitted a term
paper on the stability of thin liquid films for
Ruckenstein's graduate course in Diffusion Opera-
tions. This paper was later published and, although
not related to his Ph.D. research, it provided the
basis for Rakesh's first funded research proposal
after he later joined the faculty of Columbia Uni-
versity.
"Of course, not all of Ruckenstein's students
found this electric atmosphere to their liking. In
contrast to the more common practice of a weekly
meeting between student and advisor, the daily in-
formal discussions with Ruckenstein (sometimes
two or three times per day, including weekends)
were interpreted by some students as undue pres-
sure when, in fact, they reflected a genuine and
deep interest in and an eagerness to obtain the
results. As his students, we learned it was far
more rewarding to obtain an order-of-magnitude
answer to a new problem than to add another sig-
nificant figure to the answer of an old problem;
we learned also that it was far more exciting to


Ph.D. candidate Srinivasan in consultation with
Ruckenstein.

explain a new effect qualitatively than to predict
quantitatively an old effect in a new coordinate
system.
"Ruckenstein's approach to engineering science
is like the impressionist's approach to painting:
the goal is to capture the essence of an object or a


SPRING 1981











Never had we encountered anyone who so effervesced with ideas, who had
such deep knowledge of so many areas, or who could readily identify and explain the essence
of complex phenomena so clearly and succinctly. We soon discovered he was also a warm person
who enjoyed sharing his knowledge and ideas with others, especially students.


phenomenon without producing an exact image or
description. As photography shifted the emphasis
of art from realism to impressionism, advances in
computer technology and numerical methods will
change the emphasis of engineering science from
exact solutions of mathematical models to explain-
ing anomalies and formulating models. To meet
these new goals, a broad technical base is required
together with an appetite to learn new fields.
These are qualities of Ruckenstein which he also
instills in his students."
***
Two former graduate students at Delaware
followed Eli when he moved to SUNY at Buffalo.
One of these was Charles Dunn (now with Owens-
Corning) whose Ph.D. research at Buffalo con-
cerned the stability of thin solid films and the slip
of drops which occurs during wetting of solids.
The other was Dady Dadyburjor (now at RPI),
who did post-doctoral research with Eli on
catalysis by metals and mixed oxides. Dady pro-
vides this last vignette which describes his ex-
periences with Eli at Buffalo.
***
"As a post-doctoral fellow with Eli Rucken-
stein, life was uncomplicated, straightforward, and
busy. For him then, as now, his family, his work
and his students were and are all-important;
everything else places a very distant second.
Certainly no one associated with him has ever
had occasion to indulge in the deadly sin of sloth.
His expectations of his colleagues are high, but his
demands on himself are much higher.
"Rare was the day when I arrived at work
before him. Rain or shine or snow, he would walk
about two miles from his home to his office in the
Parker Engineering Building on the old campus.
Almost invariably he would have forgotten to eat
breakfast, so 10 o'clock would find him raiding
his brown bag. Throughout the day there would
be a steady stream of students and telephone calls;
advice, exhortations and commiserations. In the
evenings he would ride back in our car pool, Ma-
hendra Doshi (now at the Institute for Paper
Chemistry in Appleton) and Avi Marmur (now at
Technion in Israel). We held our lives too dear to


ask him to drive. A fascinating idea, or a telling
counter-argument, and he would lose sight of the
more prosaic things in life such as stopping at red
lights. After supper the work of the day would
start up again. Many was the concept firmed up
or laid to rest, and many were the bottlenecks re-
moved, when saner souls were in bed.
"Stories of his single-mindedness abound. My
own favorite concerns the time he was at the
ballet. Something on stage reminded him of a
project on which he was working. He reworked the
analysis in his mind, came up with the fallacy,
and solved the problem. From then on, his evening
was spoiled until he could get home and discharge
the contents of his mind. He went to bed shortly
before dawn, tired but satisfied.
"Eli is a man who generates ideas, who believes
that phenomena exist to be explained, and the
name of the discipline is irrelevant. This, together
with an encyclopaedic memory and an intuitive
grasp of scientific principles, have led to contribu-
tions in many areas. For example, some topics of
his doctoral students at Buffalo included sintering
and redispersion of supported metal catalysts (by
Y.F. Chu, now at Mobil), deposition of blood
platelets and the kinetics of thrombus formation
(by A. Marmur, now with Technion), stability
of thin solid films (by C. Dunn, now with Owens-
Corning), micellization (by R. Nagarajan, now at
Penn State), microemulsions (by J.C. Chi, now a
department chairman in Taiwan), structure and
phase transitions in oxides (by J. Kumar, now at
IIT, Kanpur), splitting of Pt crystallites on
alumina (by M. Malhotra), adsorption in ultra
small pores (by W.H. Chen, now at National
Cheng Kung Univ.), thermodynamics of wetting
(by P.S. Lee, now on the faculty at SUNY
Buffalo), kinetics of glass formation (by S. K.
Ihm, now at the Korean Advanced Studies Insti-
tite) and the design of pores in alumina (by K. N.
Rai, now at IIT, Kampur).
"Eli works with so much gusto that it could
be considered his hobby. If he were to admit to a
second hobby, it would probably be the study of
philosophy and the history of religion. Knowing
him to be a less than orthodox practitioner of the
Jewish faith, it surprised me when he first


CHEMICAL ENGINEERING EDUCATION








launched into an expostulation of the intricacies
of that philosophy, and its links to other religions.
Some years ago his family presented him with a
complete set of the Durants' treatises on Western
Civilization. From time to time he would keep us
posted about his advance through the series,
criticize their shortcomings, and marvel at their
insights.
"His course in Special Topics delivers exactly
what the title promises. Students work at their
own pace, reading the literature on a topic or
topics of interest to them. The odds are that Eli
has done some work in that area. To be successful,
such a course requires an instructor with a prodi-
gious command of the literature and an interest in
working one-to-one with students. From all
accounts, this course is eminently successful.
"His undergraduate classes also bear his par-
ticular stamp. There is probably as much of the
history and the philosophy of chemical engineering
as there is heat transfer in any given lecture. After
all, most of the information on heat transfer is
available in the textbook; to expound on it from a
historical perspective requires someone like Eli.
"I remember the two years I spent in Buffalo
with fondness. No one who has interacted closely
with Eli can be untouched by his warm per-
sonality."
These vignettes portray a self-taught humanist
who inspires his associates toward academic
careers by his insatiable appetite for knowledge
and understanding. While accessibility to a greater
number of more current scientific journals per-
mitted the expansion of his research horizons, and
while the greater academic freedom in the West
may have stimulated this expansion, only his
strength of character can explain Eli's successful
and rapid adaptation to academic life in the U.S.
and his remarkably broad and prolific efforts in
research. r-


conferences
APPLIED NUMERICAL METHODS
June 15-19, 1981. University of Michigan
Intensive course intended for those persons in in-
dustry and government who wish to acquire a
working knowledge of numerical methods. Presen-
tations cover a variety of numerical methods used
in the solution of practical engineering problems
and their implementation on digital computers.
Contact Engineering Summer Conferences, 300


Chrysler Center, North Campus, Ann Arbor
MI 48109

NEW DEVELOPMENTS IN MODELING, SIMULATION
AND OPTIMIZATION OF CHEMICAL PROCESSES
July 20-29, 1981 M.I.T.
Program to present basic principles and techni-
ques for computer-aided design and control of in-
dustrial-scale chemical processes. Topics: steady-
state process simulation, process optimization,
dynamic modeling and simulation of chemical pro-
cesses, computer-aided process systhesis, physical
property calculation. Contact Director of the Sum-
mer Session, MIT, Room E19-356, Cambridge MA
02139

ADVANCES IN EMULSION POLYMERIZATION AND
LATEX TECHNOLOGY
June 8-12, 1981 Lehigh University
An in-depth study of the synthesis and properties
of high polymer latexes. Subject matter will in-
clude a balance of theory and applications as well
as a balance between chemical and physical
problems. For further information, contact Dr.
Mohamed S. El-Aesseer, ChE Department,
Whitaker Lab #5, Lehigh University, Bethlehem,
PA 18015

UNDERGROUND STORAGE OF GASES
June 18-25, 1981 Boyne Falls, Michigan
Short intensive course by Katz and Tek, to be
held at Boyne Mountain Resort. Write or call E. L.
Hudge, CEEC, 2000 E. Stadium Blvd., Ann Arbor,
MI 48108 (313)764-2383 or 663-3634


book reviews

PRINCIPLES OF POLYMER PROCESSING
By Z. Tadmor and C. G. Gogos
Wiley-Interscience
Reviewed by C. D. Han
Polytechnic Institute of New York
I must point out that it is not easy to write a
textbook of polymer processing, especially for the
beginner, because the understanding of the subject
requires some knowledge of, or at least some ex-
posure to, fluid mechanics, heat transfer, rheology,
polymer chemistry, and polymer physics (morph-
Continued on page 90.


SPRING 1981









JOH MeMN Cii

JOHN C. BIERY


John C. Biery, 53, Professor and Chairman of
Chemical Engineering at the University of Flor-
ida, died in a plane crash in Gainesville, FL. on
Friday, Jan. 9, 1981. He had been chairman for
over nine years, previously teaching for one year
at the University of Arizona following seven
years at Los Alamos Scientific Laboratory. He
received his BS from the University of Michigan
and his PhD from Iowa State University. He was
Past Chairman of the ChE Division of ASEE.
These above dry facts do not convey the over-
powering feelings that flooded those who knew
and, as a result, loved John, when the tragic news
was received. An initial shock of disbelief, a
painful acceptance of its reality, but then a
glowing reflection on the goodness of John's
exuberant life. Essentially everyone has said, "You
know, the last time I saw him, we had such a good
time together."
Most of us here knew John during the time
he lived in Gainesville. His activities demonstrated
his tremendous capacity for accomplishment over
the great range of titles of professor, chairman,
AIChE and ASEE member, consultant, researcher,
jogger, pilot, seminar speaker, organizer, facili-
tator. Yet the breadth and depth level of the activi-
ties were not what was so remarkable; rather his
personal warmth and feeling and his stress on the
value of relationships among people in all aspects
is recollected.
Among the many activities in which he took
great enjoyment was working with industrial re-
cruiters. John believed deeply in the American
process of technological advancement and the


value of a technical career. His role here was
to facilitate interactions between industry and
academia, properly prepare students for the next
step in their lives and to enable his faculty to
reach their own research goals while providing
the understanding and knowledge for the next
developments in practice. In his interaction with
companies, he encouraged-no, insisted, that they
contribute to the educational process not only for
their own sake and that of the students, but also
that of society. He developed the largest program
of aid for minority students in the college, tire-
lessly badgering companies to provide funds and
summer jobs, personally counselling and often
teaching the students himself.
Though John had worked outside the Uni-
versity for much of his professional life, when
he became Chairman, he did it in his character-
istic way, with tremendous enthusiasm and per-
sonal concern for all its aspects. His prime interest
was education in its broadest sense. He was
committed to the development of the entire in-
dividual, and he recognized how all elements of a
student's life make an impact. There is no student
who was not genuinely and personally touched by
John while here. There are a tremendous number
who would say, and have said, "He is personally
responsible for the great position I am in." Even
more, he not only took great pride in his faculty,
he aggressively sought opportunities for them, he
fought for their support, encouraged them to reach
their potential and enjoyed his personal relations
with them and their loved ones immensely. In fact,
to him the faculty family clearly included the
family of faculty.
John was often involved with organizing pro-
fessional meetings on teaching and on personal
relationships, presenting papers such as "Should
Engineering Students Be Taught To Blow The
Whistle?" and "Can An Engineer Be Actualized?"
Administrators above and staff below had more
than a respect for him. John had the ability to
address problems headon while being able to show
a genuine sense of respect to the people with whom
he was working. This quality alone set him apart
and truly distinguished him as a person of high
integrity and leadership. Further, he led by
example, doing things that people could follow.
This enhanced his effectiveness and caused him to
endear himself to other people.
John's approach to life was typified by his
approach to running. He did not just jog half-
Continued on page 84.


CHEMICAL ENGINEERING EDUCATION








Chevron


Chevron Oil Field


Research Company


PhD Chemical Engineers
For Research And Development
In Enhanced Oil Recovery


Chevron's laboratory in La Habra, California is
engaged in research directed toward increased
recovery of oil and gas from known subsurface
reservoirs. Chemical engineering technology is
extremely important in the very complicated
business of recovering petroleum from known
reservoirs-reservoirs of oil and gas already
discovered and in quantities large enough to
make a real difference in the United States'
domestic energy supply. That is, if we can find
more effective processes for breaking it free
from the rocks and bringing it to the surface.
The research, the development and the field
trials of new ideas for recovering oil carry
high risks and high costs. But the stakes are
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twice as much oil is left behind as is
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stakes really are and the energy resources
that will be available if we can find the
unlocking processes.
Our chemical engineers are also
working on the problems of in situ
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If you want to learn more about
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send your resume to:


J.C. Benjamin
Chevron Oil Field Research Company
P.O. Box 446
La Habra, CA. 90631


- sva-MA


---


~CAr dO~S


/1


L";j




































department


CHE AT ROLLA


G. K. PATTERSON
University of Missouri-Rolla
Rolla, MO 65401

STUDENTS STUDYING CHEMICAL engineering at
the University of Missouri-Rolla (UMR)
benefit greatly from being on one of the foremost
engineering campuses in the country. The School
of Engineering is one of the largest and the School
of Mines and Metallurgy is among the few com-
plete schools of its type. Strong science depart-
ments with large enrollments give a solid founda-
tion for the engineers' undergraduate studies.
The University of Missouri-Rolla was first es-
tablished in 1871 as the Missouri School of Mines
and Metallurgy and operated under that name
until 1964, when the University of Missouri
system was formed. Old timers still frequently
refer to the "Rolla School of Mines." This uni-
Copyright ChE Division, ASEE, 1981


versity campus is affectionately referred to as
simply "Rolla," since no one knows of any other
place of that name.
UMR is known and respected for its strong
undergraduate engineering curricula. Even though
its departments are among the largest in the
country, the campus is recognized for the very
close contact between professors and undergradu-
ate students. This attention to the undergraduates
and their programs leads to a very enthusiastic
reception of the students by industry upon gradua-
tion. The undergraduate curricula have retained
a high degree of applied engineering content, even
while incorporating new developments in engi-
neering technology. The chemical engineering
curriculum still includes 27 hours of chemistry,
but it also includes a very current lecture and
laboratory course on industrial instrumentation
and control. Seniors can choose from a wide
variety of elective courses, including nine hours


CHEMICAL ENGINEERING EDUCATION








of polymer technology and a new polymer science
laboratory course.
The Chemical Engineering Department was
started as the Department of Chemical Engineer-
ing and Chemistry in the early 1920's. An early
leader in its development was department chair-
man, Professor Walter T. Schrenk. In 1957
Dudley Thompson became chairman of the com-
bined department. In 1964, it was divided into
the Department of Chemical Engineering and the
Department of Chemistry when the University of
Missouri multi-campus system was established.
Both are still housed in one facility, work closely
together, and offer undergraduate and graduate
programs through the Ph.D. Professor Mailand R.
Strunk became chairman of chemical engineering
in 1964 when Professor Thompson was promoted
to Dean of Faculties. Professor Strunk led the
department through its greatest period of growth,
in both undergraduate and graduate programs,
until he retired in 1979. Professor James W.
Johnson is now chairman.
The University of Missouri-Rolla is composed
of the School of Engineering, the School of Mines
and Metallurgy, and the College of Arts and
Science. Graduate work in each school is co-
ordinated by the Graduate School. The Depart-
ment of Chemical Engineering is part of the School
of Engineering. Total enrollment in UMR is ap-
proximately 5,500 students, and in the Department
of Chemical Engineering it is about 450 students.
Around 100 B.S. degrees in chemical engineering
are granted each year. About 90 per cent of UMR
students are engineering or science majors.
Most of the buildings on campus were con-
structed after 1964 and the new Chemistry-Chemi-
cal Engineering Building was built in 1973. The
teaching laboratories, research laboratories, and
classrooms are of modern design. Other recently
constructed buildings of interest to students in
chemical engineering are the Engineering Re-
search Laboratory, the Graduate Center for
Materials Research (which houses many special
purpose instruments), the Mathematics and Com-
puter Science Building (which houses the com-
puter center), the Library, and the University
Center. The library contains over a quarter million
science and engineering volumes. The computer
center is linked to the new Amdahl 470/V7 com-
puter housed in Columbia, Missouri, through its
own IBM 4331. The computer center also contains
a wide array of mini- and micro-computers for
student use, and is linked to a network of mini-


computers housed in various departments (one of
which is in chemical engineering). One center,
Cloud Physics Research, is housed in an older
building, but contains extensive facilities for
studies of cloud simulation, aerosol generation and
characterization, and cloud and aerosol flow and
mixing.
The laboratories and centers aid the depart-
ment of chemical engineering in maintaining the
range of activities necessary for a good graduate
research program. Some projects are done jointly
by students and faculty in chemical engineering
and in the centers in addition to those done com-
pletely in chemical engineering, and in many cases
the centers provide service to chemical engineer-
ing. Research is also served by a central machine
shop, a graphics and art center, and an electronics
repair shop.
Besides these campus-wide facilities, the de-
partment has a large shop staffed with two
technicians, a computer laboratory with both

In common with the rest
of the programs in engineering,
the Chemical Engineering Department
maintains an undergraduate program that
emphasizes practical engineering ... The
emphasis continues ... throughout
the curriculum.

analog and digital computers, electronics repair
facilities, key punch room, six computer terminals
linked to the University's large computer, and
heavily used copying and transparency facilities.
The department has a strong and diverse
graduate program. The master of science degree
has been offered for many years. The first doctor
of philosophy was granted in 1961. Since that
time about 300 M.S. and 60 Ph.D. degrees have
been granted. Graduate enrollment in chemical
engineering is about 40 students. Three post-
doctoral students and one research assistant pro-
fessor are currently working in the department.
About 2 to 5 Ph.D. degrees are granted each year.

ROLLA AND THE OZARKS

T HE UNIVERSITY OF Missouri-Rolla is located in
one of the most scenic areas of Missouri on
Interstate 44 mid-way between St. Louis and
Springfield. Outdoor recreational activities, such
as camping, fishing, floating and hiking, are all
readily available. Rolla is in the Mark Twain
National Forest and is within an hour's drive of


SPRING 1981









two of Missouri's famous rainbow trout hatch-
eries. The Lake of the Ozarks is a one-hour drive
and the Table Rock-Bull Shoals Lake complex is
within four hours. The famous Current River area
is one hour away.
Rolla parks and the University also provide
varied recreational facilities. The town contains
sixteen public tennis courts and several parks
totaling 220 acres. The UMR golf course is easily
available. The UMR Multipurpose Building is a
general purpose gymnasium with an indoor
swimming pool, handball/racketball courts, weight
room, basketball courts, and volleyball courts. The
sports complex includes over 100 acres of playing
fields, providing for an extremely well developed
intramural sports program which is a very im-
portant diversion for students contending with
tough engineering programs.

THE UNDERGRADUATE PROGRAM
N COMMON WITH THE REST of the programs in
engineering, the Chemical Engineering Depart-
ment maintains an undergraduate program that
emphasizes practical engineering. That emphasis
starts with the freshman chemical engineering
laboratory, which includes several experiments


The Computer Laboratory
illustrating typical chemical engineering tech-
nology, such as heat transfer, fluid metering,
pumping and power requirement, sieve-plate dis-
tillation, manometry, and fluid mechanics. The
experiments require quantitative treatment and
are not just demonstrations. The laboratory gives
the freshmen early experience in real aspects of
chemical engineering, adding meaning to required
studies of chemistry and physics.
The emphasis on practical engineering
continues throughout the curriculum. The students
are required to take a three-hour course in stoi-


chiometry, 6 hours of thermodynamics, 11 hours
of transport (fluid dynamics, heat, transfer
staged operations, and mass transfer), a three-
hour course in control and instrumentation, a
three-hour course in reactor design, six hours in
design and economic project analysis, and 3 hours
of junior level chemical engineering laboratory.
A one-hour professional orientation course is also
required. The program has a heavy component of
laboratory experience including the two-hour
freshman course, three hours of junior laboratory,
two hours of laboratory within the instrumenta-
tion and control course, two hours of physics
laboratories, and a total of 10 hours of chemistry
laboratories. Older curricula included even more
laboratory hours, but a reduction in laboratory
hours occurred when the total hours required for
the B.S. degree was reduced several years ago.
Great effort was made to retain as much labora-
tory experience as possible. Such experience is
equally valuable both for those entering industry
at the B.S. level and for those pursuing graduate
study.
An important aspect of the undergraduate ex-
perience at UMR is participation in the student
chapter of AIChE. All students are strongly en-
couraged to participate, and most find it a reward-
ing professional and social experience. The UMR
chapter has won an Outstanding Chapter Award
for the last eight years and is one of the most
active in the country. The chapter meets twice
each month when the university is in session and
has an industrial speaker at all meetings except
when officer elections are held. These programs
provide valuable orientation in the chemical in-
dustry, particularly since most speakers stress the
types of work involved in their companies. The fall
and spring outings sponsored by the chapter and
the fall mixer, which includes the chemistry de-
partment, provides social contact between students
and their professors.

THE GRADUATE PROGRAM

ROLLA'S IS A GROWING graduate program in
chemical engineering. It is growing in terms
of stature in the academic community and in
terms of funded research. The program has been
attracting a higher proportion of students from
other universities, and the research done by the
students and their professors is gradually enjoy-
ing more attention.
Since the first Ph.D. degree was granted in


CHEMICAL ENGINEERING EDUCATION










The program has a heavy component of laboratory experience
including the two-hour freshman course, three hours of junior laboratory, two
of laboratory within the instrumentation and control course, two hours of physics
laboratories, and a total of 10 hours of chemistry laboratories.


1961, the department has averaged three Ph.D.
degrees and sixteen M.S. degrees each year. From
practically no outside support for research projects
in the sixties, the funding for support from in-
dustrial and federal sources has grown steadily
during the seventies to a total of about $590,000
in outside support last year. The sources of support
include DOE (2 projects), USDA, NSF (3 proj-
ects), NASA, OWRT, USDI, NIH, and several in-
dustrial sources. As well as the industrial sources
for specific research projects, several industrial
fellowships are also available each year.
From the students' standpoint there are two
important aspects of a graduate program; the
course offering and active research projects. New
courses are continually introduced to support new
research areas and to update the curriculum.
Chemical engineering graduate students are re-
quired to take Advanced Transport and Ad-
vanced Thermodynamics, and are encouraged to
take Applied Mathematics. M.S. candidates are re-
quired to take two courses outside chemical engi-
neering. These are usually graduate or senior level
courses in chemistry, mathematics, or computer
science, but may be in any engineering or science
area that supports the individual's program. Ph.D.
candidates normally take 45-60 hours of course
work, with as much as one-half from outside
chemical engineering. Each course program is
tailored by the student and his committee to fit
the objectives of the student's educational and re-
search program.
The department also offers a special program
leading to the M.S. or Ph.D. degree for persons
with a B.S. in chemistry. The detailed require-
ments generally provide enough remedial study in
chemical engineering to give the student the engi-
neering competence of a B.S. in chemical engineer-
ing, while providing advanced study.

THE FACULTY

A N ACADEMIC PROGRAM AND its quality are es-
sentially determined by the faculty. The chemi-
cal engineering faculty at Rolla is dedicated to
the growth in the effectiveness of their research
program and to the maintenance of an already out-


standing undergraduate program. The balancing
of those two objectives is sometimes difficult. The
administration and guidance of that balancing
effort are given by our new department chairman
(as of September 1979), James W. Johnson. His
chairmanship is particularly fitting since he was
granted the first Ph.D. degree given by the depart-
ment.
In recent years, several of those who helped
develop the graduate program to its present level
have left Rolla to assume administrative positions.
Those include Robert W. Wellek, presently at DOE
in Washington, D.C., Jacques L. Zakin, chemical
engineering department chairman at Ohio State
University, Efton L. Park, department chairman
at the University of Mississippi, James L. Gaddy,
department chairman at the University of
Arkansas, and Russell A. Primrose, dean of engi-
neering at the University of Dayton. As good
teachers and researchers move to other responsi-
bilities they have been replaced by those just as
dedicated. The present faculty and their research
interests are listed in Table 1.

RESEARCH FACILITIES

An important aspect of graduate work in a
chemical engineering department is the equipment
available for research. The major equipment avail-
able in our department is in the areas of computa-


Reaction Kinetics and Equilibrium Laboratory


SPRING 1981









TABLE 1
Faculty and Research Areas
DAVID AZBEL, Professor
Nuclear reactor safety, gasification and liquifaction of
coal, hydrodynamics of two-phase systems, reactor
engineering, mass transfer.
NEIL L. BOOK, Assistant Professor
Solution of large systems of design and simulation
equations, applied mathematics, application of statisti-
cal analysis.
ORRIN K. CROSSER, Professor
Transport phenomena, applied mathematics, geometric
programming.
MARSHALL E. FINDLEY, Professor
Optimization, biochemical engineering, energy from
biomass.
JAMES W. JOHNSON, Chairman
Electrochemical oxidation, electro-organic chemistry,
corrosion.
A. I. (TOM) LIAPIS, Associate Professor
Transport phenomena, process modeling, applied
mathematics.
DAVID B. MANLEY, Associate Professor
Vapor-liquid equilibrium, thermodynamic and
transport properties.
ROBERT A. MOLLENKAMP, Associate Professor
Digital control, industrial control applications, process
modeling.
PARTHASAKHA NEOGI, Assistant Professor
Coatings under electrostatic forces, motion of fluids
in capillaries, oil reservoir processes.
GARY K. PATTERSON, Professor
Mixing, reaction engineering, turbulent fluid mechanics,
dynamic process modeling, polymer rheology.
BRUCE E. POLING, Associate Professor
Chemical kinetics, reaction engineering, vapor and
liquid properties, chemical energy storage.
X. B. REED, JR., Professor
Dispersed phase fluid mechanics, extraction, reaction
engineering, turbulent fluid mechanics, cloud physics
and cloud dynamics.
OLIVER SITTON, Assistant Professor
Biotechnology and bioprocessing, growth kinetics for
immobilized-cell systems, oxygen transfer and bio-
reactor optimization.
RAYMOND C. WAGGONER, Professor
Extraction, distillation, process control, separation
process modeling.
HIROTSUGU K. YASUDA, Professor
Plasma polymerization, polymer film permeability,
polymer adhesion.


tion, analytical instruments, thermodynamic
properties instruments, electrochemical research
apparatus, fluid mechanics research instruments,
polymer science related instruments and devices,
extraction research equipment, and equipment re-
lated to biochemical engineering research. Some of
the major units are a 24K NOVA minicomputer
with A/D and D/A capability, two UV spectro-


meters, precise L-V equilibrium apparatus, four
laser-Doppler anemometers, flash holography
system, two gel permeation chromatographs,
and multistage extraction simulation apparatus.
Within the engineering and science schools all the
usual major materials properties instruments are
also available, such as electron microscopes, mass
spectrometer, x-ray diffractometers, ESR spectro-
meter, etc.
Even though UMR is a relatively recent addi-
tion to the country's research institutions, an im-
pressive capability has already emerged. The
continued growth of research on the UMR campus
and in chemical engineering is sure to improve
that capability even more in the next decade.


LECTURE SERIES

This past year our weekly seminar meetings
were enhanced by the addition of a formal lecture
series financed by an industrial gift from the
BASF Wyandotte Corporation. In addition to
student seminars, seminars by our own faculty
and occasional visitors, six lecturers were selected
and invited to give seminars on areas of great
current interest. This will become a continuing
part of our program because of the great beneficial
effect on both faculty and graduate students.


FUTURE DIRECTIONS
Improvements in our undergraduate and
graduate programs will continue. Just as we re-
cently expanded our undergraduate fluid flow and
heat transfer course into two courses and are
adding a polymer laboratory course, other changes
to improve the curriculum will occur. The junior
chemical engineering laboratory courses will be
improved and invigorated by a complete renova-
tion of the unit operations laboratory next year. At
the same time about 2,000 sq. ft. of new graduate
research laboratory space will be created.
In the graduate studies area, we are now
seriously examining the organization of our gradu-
ate course offerings and attempting to make the
sequence of offerings more supportive of the
students' objectives. We are, of course, constantly
working to increase the level of research and
graduate student funding to insure a healthy, self-
sufficient program. Part of this effort involves
direct efforts to cultivate more and closer relation-
ships with industrial concerns that make use of
fundamental research. O


CHEMICAL ENGINEERING EDUCATION








INNOVATION...


Sometimes it's not all it's
cracked upto be.

However, at Union Carbide innovation continues to improve peoples' lives.
Union Carbide pioneered the petrochemicals industry. Today the Corporation's many hun-
dreds of chemicals are used in everything from automobile bumpers to shampoos. A leader in
the field of industrial gases, our cryogenic technology led to the development of the Oxygen
Walker System, which allows mobility for patients with respiratory diseases. Union Carbiders
are working on the frontiers of energy research-from fission to geothermal-at the world
renowned Oak Ridge National Laboratory in Tennessee. Our revolutionary Unipol process
produces polyethylene, the world's most widely used plastic, at one half the cost and one
quarter the energy of standard converting processes.
From sausage casings to miniature power cells, the Union Carbide tradition of innovation
extends beyond research and development activities to our engineering groups, manufactur-
ing operations, and sales forces.
Continued innovation will largely spring from the talents of the engineers and scientists who
join us in the 1980's.

We invite you to encourage qualified students
to see our representatives on campus-


A*
NIONDEt
B1y^


an equal opportunity employer


or write to:
Coordinator, Professional Placement
Union Carbide Corporation
270 Park Avenue
New York, N.Y. 10017











,4waud .ecdae


A FEW FUNDAMENTAL CONCEPTS AND

APPLICATIONS OF CRYOGENIC HEAT TRANSFER


The 1980 ASEE Chemical Engineering Di-
vision Lecturer was Klaus Timmerhaus of the
University of Colorado. The 3M Company provides
the financial support for this annual lecture
award.
Klaus Timmerhaus earned B.S., M.S., and Ph.D.
degrees from the University of Illinois, where he
also competed in three athletic sports; cross-
country, hockey, and track. He is still an occasional
jogger and was a member of the University of
Colorado Chemical Engineering Department's
four-mile relay team when it captured the AIChE
F. J. Van Antwerpen trophy.
After spending two years with Chevron as a
process design engineer, he joined the chemical
engineering faculty at the University of Colorado
in 1953. He presently is associate dean of engineer-
ing for graduate and research activities, director
of the Engineering Research Center, and professor
of chemical engineering. During 1979-1980 he also
served as chairman of the Department of Aero-
space Engineering Sciences.
Over the past twenty-five years Dr. Timmer-
haus has edited the Advances in Cryogenic Engi-
neering series and has coedited the International
Cryogenics Monograph Series. His work has ac-
counted for a total of 50 books and some: 70
refereed papers.
He has served as director and president of
AIChE, as chairman for the AIChE Dynamic Ob-
jectives Study, and chairman of several of
AIChE's national committees. He has also served
as executive director and chairman of the Cryo-
genic Engineering Conference Board for 12 years.
He is a member of the National Academy of Engi-
neering and a Fellow of AIChE. During 1972 and
1973 he served as section head of the Chemistry
and Energetics Section of NSF's Engineering
Division and was a charter member of NSF's Ad-
visory Council.

Coporight ChE Division, ASEE, 1981


KLAUS D. TIMMERHAUS
University of Colorado
Boulder, Colorado

Cryogenics is a term commonly used to refer
to low temperatures. However, the point on
the temperature scale at which refrigeration in
the ordinary sense of the term ends and cryogenics
begins is not well defined. Most workers in the
field have chosen to restrict cryogenics to a
temperature range below -240F (-150C or
123K). This is a reasonable dividing line since the
normal boiling point of the more "permanent
gases," such as helium, hydrogen, neon, nitrogen,
oxygen, and air lie below -150C while the more
common refrigerants have boiling points that are
above this temperature. Both the position and the
range of the field of cryogenics are best illustrated
[1] with the use of a logarithmic temperature scale
(see Fig. 1).
The entire field of cryogenics has grown
spectacularly since World War II. It is now a
major business in the U.S. with a national annual
value in excess of two billion dollars based on the
previously defined temperature range. If the
definition is broadened slightly to include the pro-
duction of some petrochemicals that utilize low


CHEMICAL ENGINEERING EDUCATION










temperature processing in their manufacture,
such as ethylene, the annual value rapidly esca-
lates to over ten billion dollars.
Cryogenics is a very diverse supporting
technology, a means to an end and not an end in
itself. For example, gases such as oxygen and
nitrogen, obtained by the cryogenic separation of
air, are very important industrial gases. Over
fifty percent of the oxygen obtained in this manner
is used in the production of steel and 20 percent
is used in the chemical processing industry. Liquid
hydrogen production, in the last three decades, has
risen from laboratory quantities to a level of over
200 tons per day, first spurred by nuclear weapons
development and later by the U.S. space program.
Similarly, the space age increased the need for
liquid helium by more than a factor of ten, re-
quiring the construction of large plants to separate
helium from natural gas by cryogenic means. The
demands for energy have likewise accelerated the
construction of tonnage base load liquefied natural
gas (LNG) plants around the world and has been
responsible for the associated domestic LNG
industry of today with its use of peak shaving


108


107


106-





10 -


103


102


10'1-


1 --


10o-'


10-2


- Hydrogen bomb

Interior of sun



Atomic explosion




Surface of sun
Iron melts
-,- Water boils
Human body temp
Water freezes
Air liquefies

Hydrogen liquefies

Helium liquefies
Helium becomes
superfluid




Adiabatic
demagnetization
temperatures
C


a Life zone





Cryogenic
temperate
range


.. the industrial liquefaction
of the permanent gases did not become
possible until the principle of efficient recovery
of the refrigeration from the cold, low-pressure
streams could be translated into engineering
practice through the development of
suitable heat exchange equipment.


plants and increasing imports of overseas LNG.
Finally, the role of cryogenics in the chemical pro-
cessing industry is aptly demonstrated with such
basic processes as the treatment of natural gas
streams to recover valuable heavier hydrocarbons
or upgrade the heat content of fuel gas, the re-
covery of hydrogen from waste gas streams, the
purification of various process streams, and the
production of ethylene.

KEY LOW-TEMPERATURE HEAT
TRANSFER CONSIDERATIONS

O NE OF THE MORE IMPORTANT aspects of any
low-temperature process is that of efficient
heat transfer. In fact, the industrial liquefaction
of the permanent gases did not become possible
until the principle of efficient recovery of the re-
frigeration from the cold, low-pressure streams
could be translated into engineering practice
through the development of suitable heat exchange
equipment. This point is rather forcibly demon-
strated by considering the effect of heat exchanger
effectiveness on the liquid yield for a simple nitro-
gen Joule-Thomson liquefaction process with lower
and upper operating pressures of 1 and 100 atm,
respectively. It can be shown that the liquid yield
under these operating conditions will be zero for
an exchanger that has an effectiveness below 90
percent even if there is absolutely no heat inleak
to the entire liquefaction system. (Heat exchanger
effectiveness is defined herein as the ratio of the
actual heat transfer to the cold stream in the ex-
changer to the maximum heat transfer possible
consistent with the second law of thermodynamics.
Most cryogens, with the exception of helium-II,
behave as "classical" fluids. As a result, it has been
possible to predict their behavior by using well-
established principles of mechanics and thermo-
dynamics applicable to many room-temperature
fluids. However, the requirements imposed by the
need to operate more efficiently at low tempera-
tures make the use of simple exchangers impracti-
cal in many cryogenic applications. In fact, some
of the more important advances in cryogenic


ire


The cryogenic temperature range.


SPRING 1981


F
2800-

212-
32-
-316 -


FIGURE 1


FIUR i










For multicomponent mixtures a temperature gradient accompanies the concentration
gradient associated with the mass transfer from the vapor phase to the liquid phase. This
results in an "effective" temperature difference between the shell and tube side which is less
than the over-all temperature difference obtained from the cooling curves.


technology are directly related to the development
of rather complex but very efficient types of heat
exchangers. Some of the criteria that have guided
the development of these units for low-temperature
service are: (1) small temperature difference at
the cold end of the exchanger to enhance the
efficiency; (2) large surface area-to-volume ratio
to minimize the heat leak; (3) high heat transfer
to reduce the surface area; (4) low mass to
minimize the startup time; (5) multichannel cap-
ability to minimize the number of exchangers; (6)
high-pressure capability to provide additional de-
sign flexibility; (7) low or reasonable pressure
drop to minimize the compression requirements;
and (8) minimum maintenance to minimize shut-
downs.
The importance of minimizing temperature
differences between streams exchanging heat and
achieving small pressure drops in each stream,
consistent with reasonable sizes and hence costs,
is clear when one realizes that these are all ir-
reversible effects which, in turn, require increased
work input. For a process as a whole we may
write
W = Wev + To m As (1)
The summation in equation (1) applies to all items
of equipment and when multiplied by the heat sink
temperature To, gives the total loss in availability
due to all the irreversible effects in the process.
Even though these losses are smaller for the heat
exchange process than the ones associated with
say the compression step, they are nevertheless
sizable and have to be made up by the expendi-
ture of expensive energy. In simple gaseous oxygen
manufacturing processes these losses may account
for as much as 13 percent of the total needed for
the cycle. The loss due to the temperature differ-
ence between two streams in a heat exchanger be-
comes even greater as the absolute temperature is
lowered. For example, at a precool temperature of
26 K in a simple Joule-Thomson helium refrigera-
tor, the optimum power required per unit of re-
frigeration increases by 32 percent as the heat
exchanger temperature difference at this tempera-
ture level is allowed to spread from 0.25 to 0.5 K.
Thus, at liquid hydrogen or liquid helium tempera-


ture, good design requires smaller temperature
differences than at liquid nitrogen or oxygen
temperatures.
The criteria of minimizing the temperature
difference at the cold end of the exchanger is not
without its problems, particularly if the specific
heat of the cold fluid increases with increasing
temperature as demonstrated by hydrogen. In such
a case, the temperature difference between the
warm and cold streams is considerably smaller in
the middle of the heat exchanger than at each end
of the exchanger. It is quite evident that the
temperature difference at the cold end wastes re-
frigeration. However, attempts to design the heat
exchanger with a smaller temperature difference
run the risk of violating the second law of thermo-
dynamics. The heat exchanger itself could not
operate under these conditions and thus the exit
temperatures would adjust themselves so that the
appropriate direction of heat flow could be main-
tained within the heat exchanger. This problem
in cryogenic heat exchangers is generally allevi-
ated by adjusting the mass flow rates of the key
stream into the heat exchanger. In other words,
the capacity rate is adjusted by controlling the
mass flow rates to offset the change in specific
heats. Problems of this nature can be avoided by
making enthalpy balances in incremental steps
from one end of the exchanger to the other.
The attainment of low temperatures, par-
ticularly on an industrial scale, has introduced
still other unique problems in heat transfer. For
example, the need for more efficient heat ex-
changer designs requires the availability of more
accurate thermodynamic and vapor liquid equi-
librium data. The analysis and evaluation of the
heat transfer process are also more complex than
usual since the physical properties of many sub-
stances at low temperatures are significantly
temperature dependent. Additionally, because of
the large temperature differences between cryo-
genic and ambient temperatures, there are fre-
quent occurrences of boiling, condensing, and two-
phase flow conditions in the heat exchangers.
Condensation of water, carbon dioxide, and other
condensable contaminants poses still another
problem that must be dealt with in cryogenic


CHEMICAL ENGINEERING EDUCATION









systems. It should come as no surprise that the
handling, transporting, and storing of cryogenic
fluids at low temperatures have necessitated the
development of specialized insulations and ap-
propriate design techniques.
Finally, one must also recognize that transient
heat transfer will be a certainty in each cryogenic
processing system until steady-state operation is
attained. Thus, the cool-down of such systems will
be an important part of the heat transfer con-
siderations and must be considered carefully in
the optimum design. Since a thorough review of
both steady-state and transient heat transfer at
low temperatures is not feasible in a presentation
such as this, we will briefly discuss a few of the
design elements that have been investigated over
the past two decades either with the help of
graduate students at the University of Colorado
or the gracious support and assistance of col-
leagues at the Cryogenics Division of the National
Bureau of Standards in Boulder, Colorado.

STEADY-STATE HEAT TRANSFER DEVELOPMENTS

T HE SELECTION OF AN exchanger for low-
temperature operation is normally determined
by process design requirements, mechanical design
limitations, and economic considerations. The
principal industrial exchangers finding use in cryo-
genic applications are (1) coiled-tube, (2) plate-
fin, (3) reversing, and (4) regenerator types.

Coiled-Tube Exchangers
These particular types of shell-tube exchangers
consist of a number of helices of small tubing
through which the high-pressure stream flows.
Cylindrical members both inside and outside of
the helices form an annular space for the low-
pressure stream. Coiled-tube exchangers offer


FIGURE 2. Industrial coiled-tube exchanger during
construction.


OUT GAS
TEMPERATURE


HEAT EXCHANGER


IN GAS
TEMPERATURE


HEAT EXCHANGER LENGTH


HEAT EXCHANGER LENGTH
FIGURE 3. Temperature profile in exchanger for even
and uneven flow distributions.
unique advantages, especially for those low-
temperature conditions where (1) simultaneous
heat transfer between more than two streams is
desired, (2) a large number of heat transfer units
is required, and (3) high operating pressures in
various streams are encountered. The geometry
of these exchangers can be varied widely to obtain
optimum flow conditions for all streams and still
meet heat transfer and pressure drop require-
ments.
One of the difficulties that may be encountered
with this highly efficient exchanger is that several
parallel paths (see Fig. 2) are used for the high-
pressure stream and thus equal flow distribution is
difficult to achieve. Likewise, on the low-pressure
side, improper spacing of the high-pressure tubes
will cause flow channeling, and again, uneven dis-
tribution. A consequence of the maldistribution
of flow is to change the local rates of heat transfer
and, hence, the local temperature distribution of
the fluid and the material in the exchanger. The
effects of maldistribution of flow on the local
temperature distribution are compared in Fig. 3
with those encountered under ideal flow condi-


SPRING 1981









tions. The curves on the right display the resulting
temperature distributions when either a negative
or a positive maldistribution in the flow of the
warm gas occurs in the exchanger. For most heat
exchangers operating at ambient temperatures the
effect of maldistribution is barely perceptible
unless there is a gross unsymmetry in the flow
passages. However, at low temperatures where
high heat exchanger effectiveness is a necessity,
maldistribution in flow of 20 percent can easily
reduce the effectiveness from 0.98 to 0.94. The
effect of such a reduction in heat exchanger
effectiveness relative to low-temperature processes
has been alluded to earlier.


FIGURE 4. Miniature coaxial tube counterflow heat
exchanger. (Courtesy of General Electric Co.)
Since the effects of flow maldistribution are
more severe in miniature exchangers, the arrange-
ment of the counterflow coaxial tube heat ex-
changer in Fig. 4 is one way to reduce the flow
channeling problems. Each of the high-pressure
tubes is contained in its own low-pressure channel,
assuring a constant hydraulic diameter for the
fluid flowing in the annuli. No unique solutions
have been proposed to date to assure even distribu-
tion of flow in large coiled-tube exchangers except
to note that great care needs to be exercised in
meeting the specified design tolerances during the
fabrication of such exchangers.
Optimization of a coiled-tube heat exchanger
design is a complex problem involving numerous
variables, e.g., tube and shell flow velocities, tube
diameter, tube pitch, and layer spacer diameter.
It can also involve consideration of single- and
two-phase flow, condensation on either the tube
or shell side, and boiling or evaporation on either
the tube or shell side. Calculations for multi-


component streams, as in natural gas liquefaction,
bring in added complications because mass trans-
fer accompanies the heat transfer in the two-
phase region.
The literature abounds with empirical relation-
ships developed to meet many of these problems
at normal temperatures. Many of these relation-
ships with appropriate modifications to the
numerical coefficients and powers have been shown
to be useful in low-temperature applications.
Studies have shown that it is difficult to predict
a priori whether one relationship will be more
suitable than another for a specific configuration
without actually making some experimental
measurements. Thus, the selected relationships
developed in our studies of industrial coiled-tube
exchangers are to be regarded as typical and not
as the only ones that could be used.
Single-phase flow of either gas or liquid on
the tube side is generally quite well represented
either by the Colburn correlation [2] or by modi-
fied forms of the Dittus-Boelter relation. For
example, one modification of the latter developed
herein for flows in helix tubular pipes for Reynold
numbers greater than 10,000 is
h = 0.023 CpG (Re)-.2 (Pr)-2/3 (1 + 3.5De/Dh)
(2)
where the fluid properties are evaluated at the
mean film temperature and D. and Dh are the
inside pipe diameter and the diameter of the helix,
respectively.
Single-phase flow of gas on the shell side (two-
phase flow on the shell side normally does not
occur in low-temperature applications) is gener-
ally handled by a modified Colburn correlation or
a modification of relations by Eckert [3] or Glaser
[4] used for normal tube banks. The correlation for
condensing two-phase heat transfer (generally
occurring on the tube side) can be based on the
relations of Davis and David [5] as modified by
Collier et al [6]. For multicomponent mixtures a
temperature gradient accompanies the concentra-
tion gradient associated with the mass transfer
from the vapor phase to the liquid phase. This
results in an "effective" temperature difference
between the shell and tube side which is less than
the over-all temperature difference obtained from
the cooling curves. Failure to recognize this re-
duction in effective temperature can result in an
exchanger with insufficient heat-transfer area.
Continued on page 98.


CHEMICAL ENGINEERING EDUCATION







"BEFORE I GRADUATED,


I HAg........
... .. .............:::.:.:: :.:: ::: ... .... .


SEVERA..........
GOOD



Joe _


Edith Whatley,
Industrial Hygienist,
Texas Division,
Dow Chemical U.S.A. =
(M.S. Chemistry,
University of Virginia)


"Choosing the right offer was a big
decision. But the more I heard about
Dow, the easier it became.
"I was impressed by how big Dow
is. But more impressed when the
interviewer told me Dow decentrali-
zation keeps you from feeling lost
in a corporate maze. He told me that
I'd be on a first-name basis with
almost everyone in my department.
"I'd also be able to contribute right
away. Because Dow thinks you learn
best by doing, and not in some formal
training program. So you get hands-


on experience from your first day
on the job.
"Plus, they encourage movement
between divisions, departments, and
even functions. So I'd get a wide
range of experience-and a chance
to find the job that's right for me.
"But I guess the main reason I
chose Dow over any other job was
that I heard of Dow's strong commit-
ment to attracting the best people.
And to giving these people the
chance to develop and grow.
"I am developing. I am growing.


I'm pleased that I chose Dow."
If you know of qualified graduates
in engineering or the sciences, or
with an interest in marketing, finance
or computer science, we hope you
will encourage them to write us:
Recruiting and College Relations,
P.O. Box 1713-CE, Midland, Michigan
48640. Dow is an equal opportunity
employer- male/female.
DOW CHEMICAL U.S.A.
*Trademark of The Dow Chemical Company
1981, The Dow Chemical Company


HERE'S


WHY













TRANSPORT PHENOMENA IN THE DELAWARE


STUART W. CHURCHILL
University of Pennsylvania
Philadelphia, PA 19104

The Great Canoe Outing on the Delaware River
sponsored annually by the Department of Chemi-
cal Engineering of the University of Pennsylvania
has become one of the rites of Spring in the
Eastern United States, fostering intra-university,
inter-university and university-industry com-
munication, and providing fellowship, recreation
and occasional sunburn, poison ivy, indigestion,
blistered hands and sore muscles.
This annual event began in 1969 when Pro-
fessor R. Byron Bird of the University of Wis-
consin was invited to give a talk in the Faculty-
Graduate Seminar Series at the University of
Pennsylvania. He declined the accompanying
challenge of a tennis match with one of the Penn


After receiving bachelors degrees in both mathematics and chemi-
cal engineering at the University of Michigan in 1942, Stuart W.
Churchill worked for the Shell Oil Company and the Frontier Chemi-
cal Company. He returned to Michigan in 1947 for graduate work
and remained as a faculty member, serving as Chairman of the De-
partment of Chemical and Metallurgical Engineering from 1962 to
1967, when he joined the University of Pennsylvania as the Carl
V.S. Patterson Professor of Chemical Engineering. His current research
interests are in combustion and natural convection. "Inertial Flows,"
the first of a series of monographs he is preparing under the
general title "The Practical Use of Theory in Fluid Flow and Heat
Transfer," has just been published by Etaner Press. His publications
also include "The Interpretation and Use of Rate Data-The Rate
Process Concept" by Hemisphere and over 150 technical articles in
journals.


The Eagle and Eaglets on the Delaware


faculty members, but responded favorably to the
invitation of Arthur E. Humphrey to go canoeing.
Art, then Chairman of Chemical Engineering,
later Dean of Engineering at Penn and now Pro-
vost at Lehigh, made all arrangements and pro-
vided enthusiastic leadership, just as he has in all
subsequent years. The event has always been held
on and in the Delaware River from Dingman's
Ferry Slip above Bushkill, Pennsylvania to Kitta-
tinny Point at the famous Delaware Water Gap
in New Jersey, 18 miles downstream. The first
year only a few Senior and graduate students,
faculty members, friends and family members
attended. Through the years the troupe has gradu-
ally expanded in scope to include students from all
classes, alumni and secretaries from Penn, and
faculty members from many of the schools in the
the area, including Carnegie-Mellon, Drexel,
Delaware, Lehigh, and Princeton. Participants
have frequently come from the AIChE and the
National Institutes of Health and from as far
away as Michigan, Israel, Guatemala and Kazak-
stan. Professor Lee C. Eagleton [see Figure] and
his colleagues at Pennsylvania State University
have been regulars.
The aforementioned stretch of the Delaware
River Valley is usually bursting into leaf and

Copyright ChE Division, ASEE, 1981


CHEMICAL ENGINEERING EDUCATION










Bob Bird enlivened the first trip with conversations in French, German, Russian
and Japanese and delivered spontaneous lectures (surreptitiously tape-recorded) on various
topics including the J-stroke, bursitis, irreversible phenomena and the length
of the sine curve traced by some of the neophyte canoeists.


blossom the last Sunday in April but is still rela-
tively deserted by mankind except for a few shad
fishermen (who openly deprecate the intrusion of
a noisy parade of canoes). The water, recently
freshened by the melting snow of the Pocono
mountains, is usually swift enough to minimize
the effort of paddling unless there is a strong
headwind. White water is limited to a few short
stretches.
The trip is broken midway for lunch on
Pocono Island. Individual luncheon fare varies
from the like of champagne and caviar served on
an especially embroidered tablecloth to diet coke
and hot dogs on the bare grass, but beer remains
the staple.
The outing is not officially a race, but the
exuberance generated by the beverages and the
end of classes at Penn usually fosters some in-
formal competitive paddling on the downriver
stretch. Each year has seen at least one ducking
in the cold waters of the Delaware but no one has
yet been lost. The spirit of Spring inevitably
tempts one or more couples to explore the wooded
shore, thereby delaying their arrival at the finish
to the point of alarm.


Honored Guest R. Byron Bird


Bob Bird enlivened the first trip with con-
versations in French, German, Russian and
Japanese and delivered spontaneous lectures (sur-
reptitiously tape-recorded) on various topics in-
cluding the J-stroke, bursitis, irreversible phe-


Warren Seider Makes a Toast


nomena and the length of the sine curve traced
by some of the neophyte canoeists.
Each year since 1969, a distinguished chemi-
cal engineer has been invited to attend the Great
Canoe Outing as Honored Guest and deliver a talk
at the Penn Faculty-Graduate Seminar the follow-
ing day. These guests have included Professors
Edwin N. Lightfoot, Dale F. Rudd, Camden A.
Coberly, Warren E. Stewart and Thomas W. Chap-
man, all of the University of Wisconsin, Professor
James J. Carberry of the University of Notre
Dame, Professor Edward L. Cussler, Jr., of
Carnegie-Mellon University and Professor H. Scott
Fogler of the University of Michigan.
Professor Lightfoot commemorated his par-
ticipation in the Great Canoe Outing of 1970 with
the gift of a brightly painted canoe paddle graced
with the jingles:

A HEMULEN AT HEART
Your host is a pusher named Art
Who believes in an organized start,
and lest you relax
to rest aching backs
You must portage before you depart.


SPRING 1981









THE TIE-ON DEAL
Penn harbors a hatter named Stu
Who thinks that in every canoe
with beauty and lunch
should be a gay bunch
Of hats that small bats could fly through.

In return he was presented with a headdress and
Birdsfoot [see Figure]. This paddle has subse-
quently been designated as the Edwin N. Lightfoot
Up-the-Delaware-without-a-Canoe Paddle, and
each year is inscribed with the name of the out-
standing performer or performers during the out-


Ed Lightfoot with Headdress and "Birdsfoot"


ing. It was awarded retroactively for 1969 to
Hiroyuki Ozoe who steered a three-man canoe
deeply into the reeds of a backwater during a
competitive sprint to the finish line. In 1970 it
went to Mike McKetta (Johnny's son) who went
to the extreme of seizing and throwing away a
paddle and finally trying to overturn the canoe
occupied by the Honored Guest rather than be
passed. In 1971 Peggy Lempa and associates
earned the honor by all three falling in the river
while embarking and then, after they had dried
off and resumed, being swamped and overturned
by the wake of a motor boat. The 1972 winners
were Aaron and Tina Weiner who chickened out
in a stretch of white water, beached on an island
and abandoned their canoe to the river. Its empty
appearance frightened everyone and forced Art
Humphrey and Cam Coberly (the Honored Guest)


These (Honored Guests) have
included Professors Edwin N. Lightfoot,
Dale F. Rudd, Camden A. Coberly, Warren E. Stewart
and Thomas W. Chapman .. James J. Carberry ...
Edward L. Cussler, Jr.,...
and H. Scott Fogler.


to paddle and portage upstream for their rescue;
thereby being designated as winners in advance
for 1973.
Other winners of the Lightfoot Trophy include
Renate Treibmann, who lost her paddle between
the canoe and a boulder only to have it fly into the
air and directly into the hands of another canoeist;
Bob Dedrick and Bob Lutz, who proudly demon-
strated the superiority of kayaks by turning com-
plete circles around canoe after canoe as they
passed them; John Goepp who "accidentally" over-
turned twice while secretly wearing a wet suit;
Andrew diLemmo who demonstrated his Tarzan
technique by swinging on a huge vine throughout
the lunch break only to discover that it was poison
ivy; James J. Carberry, who as the Honored Guest,
arrived a day late, perhaps taking to heart the
outing motto of that year by his idol Dante
Alighieri-"Lasciate ogni speranza voi ch'entrate";
and an anonymous canoeist who fell in, frightened
everyone by failing to resurface, and was subse-
quently discovered to be hanging on desperately
in the air pocket under the overturned canoe.
The U.S. Army Corps of Engineers has long
plotted to dam the Delaware River at Tock's
Island, just above the Delaware Water Gap,
thereby turning the site of the Great Canoe Outing
into a reservoir. This threat now appears to be
postponed indefinitely in deference to the environ-
mentalists, but has been replaced by another. Our
recent departmental chairman became addicted to
long-distance running, and in 1978 he and several
students split from the canoeists at lunch time and
ran the remaining 9 miles along the New Jersey
shore. Naturally they were forced to abjure the
amenities of food and drink on the island and to
leave their canoes to be ferried down the river
by others. This diversion was repeated in 1979,
and only time will tell whether or not the Great
Canoe Outing will be supplanted by a Delaware
Water Gap Mini-Marathon.
All chemical engineers and friends everywhere
are welcome to join us some year on the Great
Canoe Outing (and/or Run). 0


CHEMICAL ENGINEERING EDUCATION












Process Analysis and Advanced Process
Design for Chemical Control
Engineers W. Harmon Ray, University of
Wisconsin, Madison
William Resnick, Technion 416 pages, $29.50
Israel Institute of Technology Appropriate for advanced
400 pages, $25.50 undergraduate and graduate
This new book combines the undergranawe w dst
This new book combines the students as well as practicing
elements of modern process control engineers who must
engineering and design with design economically optimal
those aspects of traditional process control schemes, this
chemical engineering that need book presents a comprehensive
emphasis in light of the design introduction to the theory and
and analysis functions of the practice of modern computer
chemical engineer. process control.
Principles of Polymer
Systems, 2/e, (Available in
1981, with a 1982 copyright.) From O ur
Ferdinand Rodriguez,
Cornell University 980 List
576 pages (tent.), $27.95 (tent.)
Emphasizing quantitative
description of polymers and Separation
manipulation of data to predict Processes, 2/e
and correlate the behavior of C. Judson King
real polymer systems, the new C. Judson King,
second edition includes the most University of California, Berkeley
current figures, references, and 864 p $28
text material. Plant Design and
Chemical Engineering t Economics for
Kinetics, 3/e Chemical
J.M. Smith, University Engineers, 3/e
of California, Davis
704 pages, $27.95 Max S. Peters and
Thoroughly revised Klaus D. Timmerhaus,
and updated, the both of the University of
new edition of this Colorado, Boulder
successful text 944 pages, $28.50
continues to am- Heterogeneous
phasize the application
of the principles of Catalysis in Practice
reactor design to mH i l Charles N. Sotterfield,
real chemical 0 Massachusetts Institute of
systems. Technology
432 pages, $26.95
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Egn Operations, 31e
The late Robert E. Treybal
800 pages, $26.50

Prices subject to change.
COLLEGE DIVISION
McGraw-Hill Book Company
1221 Avenue of the Americas
Ema New York, N.Y. 10020


..... .... ....
W.


..... ... .. ... .









curriculum


COMPUTER-BASED INSTRUCTION:

IS THERE A FUTURE IN ChE EDUCATION?


MORDECHAI SHACHAM* and
MICHAEL B. CUTLIP
University of Connecticut
Storrs, Connecticut 06268

AS THE WORLD ENTERS the decade of the 1980's,
revolutionary developments are continuing in
many areas of human endeavor. Unfortunately,
improvements in the delivery of university level
education has been disappointingly slow. Even
though some new tools like overhead and slide
projectors, tape recorders and television equip-
ment have been introduced into educational institu-
tions, the basic form of teaching remains the
traditional lecture.
Recent increases in enrollment in most chemi-
cal engineering departments have helped to indi-
cate that the lecture method of educational de-
livery has some serious limitations. As course
sections have become larger it is increasingly diffi-
cult, or even impossible, to personally interact
with each student to aid in the understanding of
the lecture material. Thus, the shortcomings of
the lecture system are becoming painfully ap-
parent. During a lecture the majority of the
students listen passively while only a few students
ask questions or actively answer questions. Studies
in psychology [1] have shown that, for the average
student, passive listening is a very ineffective way
to learn.
In 1968 Dubin and Taveggia (cited in Kulik
and Kulik [2]) reviewed all comparative research


... the shortcomings of the lecture
system are becoming painfully apparent.
During a lecture the majority of the students listen
passively while only a few students ask questions
or actively answer questions.


*On leave from Ben-Gurion University of the Negev,
Department of Chemical Engineering, Beersheva, Israel
84120.


on college teaching methods conducted during the
years 1924-1965. They found many studies that
utilized final examination performance as a
criteria of teaching effectiveness, and they
concluded that no teaching methods were sig-
nificantly better than the traditional lecture.
Fortunately two developments that have been
made since 1965 will have a direct impact on the
delivery of educational materials. These are:
The Personalized System of Instruction, PSI.
Computer-Aided Instruction, CAI.
This paper will provide a summary of the
essential characteristics of PSI and will provide
a detailed overview of one of the most advanced
CAI systems, the PLATO educational computer
system. A consideration of the future of computer-
based education which effectively combines PSI
with CAI will be followed by a discussion of the
current status and future use of PLATO in chemi-
cal engineering education.

SELF-PACED INSTRUCTION

T HE MERITS OF A SELF-PACED, or personalized,
system of instruction (PSI) have become
widely recognized since the initial concepts of this
method of instruction were developed by Keller
[3]. Many of the unique aspects of this type of
course presentation are summarized in Table 1.
An interesting collection of papers related to PSI
has been published by Sherman [4]. There is no
doubt that self-paced instruction provides a
superior educational experience and is preferred
by most students. Some of the strong points of
PSI are:
* Student responds and there is immediate reinforcement
or feedback
Student progresses at his own rate
Material is presented in small carefully sequenced steps
Program leaves a record leading to improvement
Punishment is minimal
Desired goals are defined and mastery is required

Copyright ChE Division, ASEE, 1981


CHEMICAL ENGINEERING EDUCATION


USShsH























Michael B. Cutlip is an associate professor and head of the Chemi-
cal Engineering Department at the University of Connecticut in Storrs,
CT. He has a Ph.D. in Chemical Engineering from the University of
Colorado. In addition to his interest in computer-based education,
he is involved with research in Chemical Reactor Engineering par-
ticularly in Heterogeneous Catalysis. He is active in the American
Institute of Chemical Engineers and is an industrial consultant. (R)
Mordechai Shacham is an associate professor in residence of
Chemical Engineering at the University of Connecticut in Storrs, CT.
He is on two year's leave from the Ben Gurion University of the
Negev, Israel. He has a D.Sc. in Chemical Engineering from the
Technion, Israel Institute of Technology. In addition to his interest
in computer based education he is involved in research in chemical
process simulation, design and synthesis, and numerical methods. (L)


At the University of Connecticut, Professors
Howard and Stutzman offered a Process Dynamics
and Control course via self-paced instruction in
1972 and 1973, but computer-based instruction
was not used. A summary of the successful ex-
perience with this course has been given by
Howard [5]. Unfortunately, the format of this
course reverted back to the traditional lecture style
of delivery because of two major difficulties: The
increased work load on the instructors was ex-
horbitant, and class sizes began to increase and
the necessary graduate assistants (tutors) were
difficult to obtain. These problems have also forced
others who prefer PSI to abandon it [6]. In addi-
tion, there are always a few students who fall
behind, procrastinate and take incomplete.
Computer-based delivery of courses can retain
most of the benefits of PSI while freeing the course
instructor from repetitive administrative details
and providing the student with an intelligent tutor.
Bitzer [7] has recently reviewed the develop-
ment of CAI, and an excellent summary of CAI in
chemistry is available (Lower et al. [8]). A recent
report entitled "Computer Graphics in Chemical
Engineering Education" [9] provides a summary
of existing applications and a thorough discussion


of current hardware and software, but this report
is only concerned with computer graphics.
The following description is limited to one of
the most available CAI systems, the PLATO
system. This advanced educational system is
widely used and seems to provide the greatest
potential for extensive utilization in chemical
engineering education.

THE PLATO SYSTEM
PLATO, an acronym for Programmed Logic
for Automated Teaching Operations, was de-
veloped during a project started in 1959 at the
University of Illinois. Since 1967, Control Data
Corporation (CDC) and the Computer-based
Education Research Laboratory (CERL) at Il-
linois have produced one of the first large-scale
computer-based educational systems. Over six
thousand hours of instructional materials are
currently available in a wide variety of fields from
interconnected PLATO computer systems located
in Minnesota, Delaware, Florida, Texas, Illinois,
Quebec and Brussels.
A schematic diagram showing the essential
features of a PLATO system is shown in Figure
1. The system is typically composed of several
central processing units (CPU), and a number of
peripheral processing units (PPU) tied to the
central memory (CM). The extended core storage
unit (ECS) is a random-access electronic
swapping memory which is tied directly to CM
and the PPU's. The PPU's handle input and out-
put to terminals and control mass storage units
such as disks and tapes and other external I/O
devices.
The new Delaware PLATO system [10] is based
on a Control Data Corporation Cyber 173 com-
puter. It is configured to service 100 simultaneous
PLATO users, but this can eventually be expanded
to 1008 users. The initial Delaware system has one
TABLE 1
Key Concepts of the "Keller Plan" for PSI
A. Individually Paced
divided into 15 to 20 units
detailed study guides provided
B. Mastery Oriented
C. No Punishment for Failure
D. Proctors Deliver Course
repeated testing
immediate scoring
unavoidable tutoring
provide personal/social aspects
E. Stress upon Written Materials
lectures optional


SPRING 1981
























FIGURE 1. PLATO computer system configuration.
CPU and ten PPU's operating with 98,000 60-bit
words of central memory. In addition, 500,000
words of extended core storage, four dual-density
disk drives, two tape drives and two remote job
entry stations are utilized.
The computer interface unit provides data
communication between the central computer and
up to 32 site controllers. The site controller pro-
cesses two-way digital data between the computer
interface unit and the PLATO terminals. The link
to the terminal may be via direct connection or
phone line. In some cases, output data to the
terminals may be multiplexed onto a standard TV
channel by the computer interface unit for efficient
transmission via microwave or cable to the site
controllers [7].

THE TERMINAL
The PLATO terminal available from Control
Data Corporation consists of a video-scan cathode
ray tube (CRT), a touch panel on the CRT, and an
electronic keyboard. The CRT display panel
contains a matrix of 512 by 512 separately ad-
dressable points. Display memory storage and
logic control of the terminal is provided by a
micro-processor located within each terminal. The
touch panel on the CRT display is capable of
sensing any one of 256 positions which allow
very convenient user input to the system. Normal
input is via the keyboard unit which has 64 key-
switch locations and is based on the typical type-
writer configuration. In addition, two sets of
arithmetic keys and special control keys are pro-
vided. Since the PLATO system interprets in-
dividual key selection before they are displayed,
authors can generate their own set of 126 charac-
ters (such as Greek letters and special symbols
like AT, 0C, e etc.).


. 258

o.299


o 3 2


g 188 Zf8 3BB 488 5BB
No. 1 2 3
L 2 1.5
"k- B.B885B6 .8 4121 8.B1872
Var 8.882777 B.8016677 B.BBI1751
Choose a single letter to:
a.Clean the whole screen. b.ChooK a ne value for n.
cChoose a new value for k. d.Record the best values of k.n.
FIGURE 2. Determination of the reaction order and rate
constant from experimental data using
PLATO.


CHEMICAL ENGINEERING EDUCATION


When a PLATO lesson is requested by a user
at a terminal, it is transferred from the disk unit
of mass storage to the extended core storage,
where it remains while in use. Programs and data
in the ECS are transferred in and out of central
memory during lesson execution. This rapid
transfer rate of the ECS makes possible a maxi-
mum response time of 0.25 seconds to each
terminal user.
A number of accessories can be attached to
the terminal. These include a random access audio
device, color microfiche slides, hard copy printers
and floppy disks. Other devices can be electron-
ically connected to PLATO such as carousel pro-
jectors, oscilloscopes, electronic test equipment and
even laboratory instrumentation.

IMPORTANT FEATURES OF PLATO
Ease of use
Neither the students nor the instructor need
to have any previous computer experience. All
that is required is an ability to use the typewriter
keyboard. Lessons are available for terminal in-
structions once the user is shown how to log onto
the system. Only five to ten minutes of terminal
time is required to learn to use the terminal.

System flexibility
The terminal users may work on different











The CMI system analyzes the students' current status, what units of the course he has
already mastered and in which areas he has had difficulties . The instructor has immediate access
to the student records and can easily do any type of statistical analysis of student performance.


lessons at the same time. It is possible for some
of the terminals to be used by students taking
lessons at the same time that others are used by
authors preparing or revising lesson material.

Student/instructor interaction
The terminal users can communicate via the
PLATO system. For example, a student may ask a
question by typing in the identification code of his
instructor and his question. The instructor can
respond immediately if he is working at a terminal
at the same time, or the next time he signs on a
terminal. The instructor may even look at the
students display or show him something which is
on his display. Their geographic locations can be
thousands of miles away from each other.

Use of the computer as a calculator
It is possible to use the terminal as a calculator
in any stage of the lesson execution. For typical
problem solving in an engineering course, this
feature conveniently allows a student to make
intermediate and final calculations. A major ad-
vantage over the hand-held electronic calculator
is that the entire function being evaluated is re-
tained on the terminal display.

Touch response
The touch sensitivity of the PLATO terminal
panel adds a new dimension to the capabilities of
CAI. In Figure 3, for example, the touch panel is
used for minimization of an objective function of
two variables. The student touches the area which
seems to be most promising as a possible mini-
mum, and PLATO evaluates the objective function
value at this point. The touch panel has also been
used to "synthesize" complex molecules from
simple ones, to test the student familiarity with
diagrams and to simulate laboratory experiments.

Graphics
The graphic and animation capabilities of
PLATO add greatly to the effectiveness of CAI.
For example, when the student tries to fit reaction


Current values: k-8.12167,n-l.625,var.-.1g1ig55


gS.22





03


*.B161 1. 1, I ,1 I 1 1. 1 I 1 I
1.2 3 1.32 1.44 1.56 1.66 1.8
Order of the reaction (n)
Touch a square to obtain the percent change of the variance
relatively to the center position.
For additional options press DATA.
FIGURE 3. Minimization of a function of two variables
using the touch panel.
rate constants and orders of reaction to experi-
mental data in a kinetics lesson, he gets both
visual and numerical feedback regarding the
goodness of fit (see Figure 2).

Analysis of the student's response
One of the more critical aspects of any CAI
system is the one that analyzes and judges the
students' responses. Nothing can be more frustrat-
ing for the student than the rejection of his correct
answer because he did not enter it in the form an-
ticipated by the author (for example, by writing
0.333 for 1/3). The PLATO system can recognize
numeric matches independent of format and can
separate the numeric part of the answer from the
non-numeric parts (when both the numerical
value and the units of the answer should be
checked). It can indicate mispellings, incorrect
answers or incorrect order of words in sentences.

Computer managed instruction (CMI) system
This software system keeps track of the pro-
gress of each individual student as well as on the
progress of the whole course. The CMI system


SPRING 1981








analyzes the students' current status, what units
of the course he has already mastered and in which
areas he has had difficulties. Prescriptions for
lessons to help achieve mastery learning can be
automatically generated on the basis of appropri-
ate testing. The instructor has immediate access
to the student records and can easily do any type
of statistical analysis of student performance. In
this manner the instructor can become familiar
with abilities of the different students, and he can
also evaluate the instructional material. For
example, when there is an exam which most of the
students fail at their first attempt, the exam must
be too difficult. Relative effectiveness of different
types of instructional material can be compared,
and the course material can be steadily improved
using this feedback.

The TUTOR language
The PLATO lessons are written using the
TUTOR language which was developed solely for
CAI use. Its developers tried to make the lesson

The reluctance of some faculty
members to use someone else's computer-based
materials will be a substantial barrier to the
implementation of computer-based materials.

writing as simple as possible. The most impressive
parts of the language are those dealing with
graphics, animation and student response analysis.
Sophisticated effects can be generated by relatively
simple and short coding. It should be noted, how-
ever, that for engineering education the calcula-
tional capabilities of the TUTOR language are
somewhat limited.
Basic knowledge of the TUTOR language can
be attained with about 85 hours of training, even
for those who have no previous programming
experience. But, of course, additional study is
necessary to use most of the TUTOR capabilities
effectively
The development of the courseware for uni-
versity level education is limited at the present.
Many separate lessons in chemistry, physics,
mathematics and other areas have been developed
at the University of Illinois and several other uni-
versities but only limited experience in the develop-
ment of a completely computer-based course has
been attained. When used in the classroom, most
current PLATO lessons either replace the regular
homework assignments or simulate laboratory ex-


periment to provide the background for the actual
experiments in the laboratory.
College students who have had the opportunity
to use PLATO are very enthusiastic about it. Their
opinion is that they have learned more, in a more
enjoyable way, than they would have through
traditional methods.

PLATO IN CHEMICAL ENGINEERING

T HE MOST ACTIVE AND ADVANCED development
of chemical engineering lessons via PLATO is
currently in progress at the University of Illinois
under the direction of Prof. Charles A. Eckert. A
complete set of lessons is being used with a first
chemical engineering course entitled "Introduc-
tion to Chemical Engineering."
PLATO lessons at Illinois replace only some
of the homework in a traditional lecture-recita-
tion type course. Students are required to com-
plete conventional homework assignments. PLATO
is not presently used for any examinations. Pro-
fessor Eckert [11] believes "that the major
effectiveness of the PLATO lessons is in per-
mitting students to do a wider variety of problems
in a short time with instantaneous interaction in
a nonintimidating manner."
At Illinois, well-written lessons prove to be
excellent motivators, and the students do the avail-
able lessons with a very high completion rate.
Students spend approximately 2/3 of their time
on new PLATO lessons and about 1/3 of their
time reviewing materials in preparation for
examinations. Performance on examinations has
dramatically increased since the introduction of
the PLATO lessons. This success has prompted
Prof. Eckert to begin working on a set of lessons
for a first course in chemical engineering thermo-
dynamics as well as some lessons on unit opera-
tions. Clearly, Prof. Eckert is very enthusiastic
about the future of PLATO.
The University of Delaware originated a
PLATO project in the Fall of 1974, and university-
wide use of PLATO was sufficient to justify the
purchase of a PLATO system in 1978 [10]. Chemi-
cal Engineering activities began last year under
the direction of Professors Stanley Sandler and
Robert Pigford. Professor Sandler is developing
PLATO lessons for several types of chemical
engineering thermodynamics problems that have
been troublesome for weaker students. Professor
Pigford is interested in lessons on material and
energy balances.


CHEMICAL ENGINEERING EDUCATION









In addition to the chemical engineering lessons
discussed above, there are some lessons in related
areas available on the PLATO system. These
lessons can be used for reviewing background
material in Chemistry, Thermodynamics and
Numerical Analysis. There are some lessons which
can make problem solving easier and make it
possible to get an immediate graphical representa-
tion of the solution. There are explicit and implicit
function plotters, a differential equation solver
and a lesson for root locus and frequency response
graphical plotting. Thus, even though the present
number of available chemical engineering lessons
is limited, the PLATO terminal can already be
a considerable aid to the education of chemical
engineering students.

A COMPUTER-BASED COURSE IN CHEMICAL
REACTION ENGINEERING

A T THE UNIVERSITY OF Connecticut, we are
directing our initial effort in the area of
chemical reaction engineering. We plan to pre-
pare PLATO materials over the next several years
so that we can eventually offer a completely self-
paced course to undergraduate students with com-
puter-based instruction. This course was chosen
because of the highly mathematical nature of the
subject material. It has traditionally been taught
with considerable use of computer programming
for problem solving and simulation.
The course material will comprise the follow-
ing:
A CMI Router which gives the student his assign-
ments according to the material which has been
completed.


FIGURE 4. Structure of the computer aided CRE course.


The more basic courses in chemical
engineering ... will eventually be offered as
self-paced computer-based courses delivered on
interactive graphical computer terminals
and utilizing self-paced textbooks,
video cassettes, audio cassettes
and film strips.


A Self-Paced textbook (probably the textbook by
Fogler [12]).
PLATO tutorial lessons for the more basic materiaL
Homework assignments on PLATO.
Examination questions and problems on PLATO.
Reactor modeling and simulation requiring numeri-
cal analysis via PLATO.
Video-taped Lectures.
The proposed structure of the course and an
approximation of the division of the student's
time between the different activities is shown in
Figure 4.
We at Connecticut feel that the present PLATO
capabilities with the acknowledged benefits of self
paced instruction will result in a greatly improved
learning experience for our students.

LOOKING TOWARD THE FUTURE
COMPUTER-BASED EDUCATION will initially de-
velop as a means of providing supplementary
materials to the more traditional lecture format
courses. In the laboratory, more and more of the
laboratory experiments will be set up and simu-
lated on interactive graphical terminals before
actual work is undertaken. Many difficulties will
be associated with the transfer of course materials
among universities because of hardware differ-
ences and software incompatibilities. The re-
luctance of some faculty members to use someone
else's computer-based materials will be a sub-
stantial barrier to the implementation of com-
puter-based materials.
The introduction of computer-based materials
will be initially resisted by most of the professors,
but enthusiastically greeted by the students who
prefer many aspects of this type of coursework
delivery. State legislatures will support the
initially high costs of computer-based instruction
because this type of delivery will allow the efficient
delivery of many introductory courses into every
community college, state college or university
branch campus in the state.
The more basic courses in chemical engineer-
ing such as Material and Energy Balances,


SPRING 1981









Thermodynamics, Process Dynamics and Control,
and Reaction Kinetics will eventually be offered
as self-paced computer-based courses delivered on
interactive graphical computer terminals and
utilizing self-paced textbooks, video cassettes,
audio cassettes and film strips. Student exposure
to completely computer-based courses will be
limited to one, or at most two, per university
term. Faculty will continue to teach advanced
undergraduate and graduate courses in the tradi-
tional lecture mode, and they will have more
time for research and personal interaction with
students. E[

ACKNOWLEDGMENTS
The cooperation and advice of Professor L. F.
Stutzman and the support of the Control Data
Corporation for the UCONN-PLATO project in
Chemical Engineering are sincerely appreciated.


REFERENCES
1. Leuba, R. J. and G. H. Flammer, "Self Paced In-
struction: Hello, Education," Engineering Education
66, 195 (1975).
2. Kulik, J. A. and C. C. Kulik, "Effectiveness of the
Personalized System of Instruction," Engineering
Education 66, 228 (1975).
3. Keller, F. S., "Good-bye Teacher," Journal of
Applied Behavior Analysis, 1, 78 (1968).
4. Sherman, J. G., Personalized System of Instruction-
41 Germinal Paper, W. A. Benjamin, Inc., Menlo
Park, California (1974).
5. Howard, G. M. and L. F. Stutzman, "A Self-Paced
(PSI) Process Dynamics and Control Course,"
A.I.Ch.E. 74th National Meeting, New Orleans,
March (1973).
6. Heimback, C. L., "To PSI and Back," Engineering
Education, 69, 399 (1979).
7. Bitzer, D., "The Wide World of Computer-Based
Education," Advan. Comput., 15, 239 (1976).
8. Lower, S. Gerhold, G. Smith, S. G., Johnson, K. G.,
and J. W. Moore, "Computer-Assisted Instruction in
Chemistry," Journal of Chemical Education, 56 (4),
219 (1979).
9. Carnahan, B., R. S. H. Mah and H. S. Fogler, "Com-
puter Graphics in Chemical Engineering Education,"
CACHE Report, Cambridge, Massachusetts (1978).
10. Hofstetter,,F., "Third Summative Report of the Dela-
ware PLATO Project," University of Delaware,
Newark, Delaware (1978).
11. Eckert, C. A., Personal Communications, Depart-
ment of Chemical Engineering, University of Illinois,
Urbana, Illinois, October (1978) and March (1979).
12. Fogler, H. S., The Elements of Chemical Kinetics
and Reactor Calculations (A Self-Paced Approach),
Prentice-Hall Inc., Englewood Cliffs, New Jersey
(1974).


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JOHN BIERY
Continued from page 60.
heartedly around the neighborhood from time to
time. He immersed himself in running, rarely
missing six to nine miles a day, studying it, ex-
perimenting with it, wiring himself up to measure
what physiological responses occurred, and getting
other people involved, mostly by the infectious
quality of his enthusiasm.
A close associate at Los Alamos summed up
many of the feelings of those close to John. "You
have been truly one of those who made the world
a better place. You gave many people a model of
how life should be lived: your zest for experienc-
ing new things and trying new ways was inspira-
tional. I am intensely grateful that you came into
my life. I just wish you hadn't left so soon."
JOHN O'CONNELL
U. of Florida


CHEMICAL ENGINEERING EDUCATION









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l classroom


USAGE OF MULTIPLE-CHOICE EXAMINATIONS

IN CHEMICAL ENGINEERING


JUDE T. SOMMERFELD
Georgia Institute of Technology
Atlanta, Georgia 30332

T HIS ARTICLE DESCRIBES extensive experience
with the usage of multiple-choice examinations
in various undergraduate chemical engineering
courses at Georgia Tech over the past four years.
A number of factors, quantitative and qualita-
tive, have led the author to experiment with such
examinations.
First, the student/faculty ratio at Georgia
Tech is higher than at most other schools and
this ratio has increased over the past five to six
years. The addition of nine faculty last year (six
new slots and three replacements) has brought
some relief but the student/faculty ratio is still
high.
Undergraduate enrollment in chemical engi-
neering at Georgia Tech today is about 1000, up
from just over 300 in 1974-75 [1]. A full-time
work load is defined by the Board of Regents of
the University System of Georgia in terms of


Jude T. Sommerfeld has been a professor of ChE at Georgia
Tech since 1970. He teaches courses on process control, distillation,
reactor design and process design, and his research interests include
energy conservation. He also served as a consultant to numerous
industrial organizations. Prior to 1970 he had eight years of engi-
neering and management experience with the Monsanto Company and
BASF-Wyandotte Corp. Dr. Sommerfeld received his B.Ch.E. degree
from the University of Detroit, and his M.S.E. and Ph.D. degrees in
chemical engineering from the University of Michigan.

0 Copyright ChE Division, ASEE, 1981


It is most disturbing ... to hear
from students, near or upon graduation,
that they have earned their engineering degree
on the basis of partial credit.


100% teaching as 15 hours per week. Since most
engineering courses carry three credit hours, this
official load translates to five courses or sections
per quarter.
Teaching loads in chemical engineering are
reduced below this five-course level based on
faculty efforts in student counseling, research and
direction of graduate students, paper and proposal
preparation, administration and service. Thus,
most chemical engineering faculty have been re-
sponsible for one or two courses per quarter
during the past year.
The combination of increased student numbers,
not enough faculty and a commitment to improve
our graduate program has led, however, to large
class sizes (one or two classes per quarter have
in excess of 100 students). Thus the grading of
examinations in our engineering courses has be-
come a rather ponderous task, particularly if the
examinations are to be returned to the students
within a reasonable period of time. The usage of
multiple-choice examinations, especially when
computer scoring of the examinations is employed,
obviously facilitates the grading process, in com-
parison with conventional problem-based engineer-
ing examinations. It should be appreciated, how-
ever, that a considerably greater amount of effort
is required at the front end of the process, that is,
in the actual construction of multiple-choice
examinations for engineering courses. This point
should become quite apparent in later sections of
this article.
From a qualitative point of view based upon
several years of experience, the author feels that
multiple-choice examinations are superior to con-
ventional problem examinations for a number of
chemical engineering courses. Using a larger


CHEMICAL ENGINEERING EDUCATION









number of relatively brief exercises in a multiple-
choice format allows the instructor to examine
the students on more concepts. Admittedly, com-
plex problems cannot easily be handled with such
an examination format, but they can be accom-
modated through homework assignments and
classroom discussion. Another positive feature of
a multiple-choice format is that it encourages
students to arrive at correct answers, a facility
that is all too often lacking in many engineering
students. It is most disturbing to engineering pro-
fessors to hear from students, near or upon
graduation, that they have earned their engineer-
ing degree on the basis of partial credit. Most
practicing engineers, after all, are employed or
engaged to provide correct or reasonable answers
given economic or other constraints.
The computer scoring of multiple choice
examinations is completely fair; the computer is
not biased by the neatness of the problem solu-
tions nor is it influenced by the personality of the
student. "Grade bargaining" at the conclusion of
each examination is eliminated since no partial
credit is granted. The learning process of the
examination is enhanced when the exercises are
assigned for homework immediately following the
examination period. The student records his/her
methodology for solving the exercises; at the next
class period the students may then compare their
solutions to the correct solutions as presented in
class.

EXAMINATION FORMAT

T HE NUMBER OF EXERCISES used in a given
multiple-choice examination obviously depends
upon the level of the associated course and on the
duration of the examination. Lecture periods in
engineering at Georgia Tech are of nominal length
of 1 or 1-1/2 hours. Thus, for a 1-hour examination
period, a total of 20-25 exercises would typically
be employed in the construction of a multiple-
choice examination. If the examination period is
1-1/2 hours long, then a total of 25-30 exercises
would be more typical. Final examination periods
at Georgia Tech are of nominal duration of three
hours. Thus, a typical figure for the number of
exercises in a multiple-choice final examination
would be 50.
The instructor must also assign values or
weights to correct answers and, if desired, penal-
ties to incorrect answers. There is, of course, no
requirement that the weights and/or penalties be


identical for all exercises. Commonly used values
of weights for correct answers are 4 or 5, while a
typical penalty value is 2 (there is some discussion
as to whether such a penalty value is too high).
Unanswered questions neither add or detract any-
thing to or from the student's score. While most
such multiple-choice examinations are usually de-
signed so that a perfect score corresponds to a
convenient value such as 100, 150 or 200, this facet
is not absolutely essential. Examination scores can
always be normalized to a reference value such as
100. Again, if the scoring is performed via com-
puter, this normalization procedure represents no
additional effort. Below are presented typical
exercises which have been employed in multiple-
choice examinations in four of the required chemi-
cal engineering courses in the curriculum here at
Georgia Tech.

MATERIAL BALANCES

A S AT MOST OTHER chemical engineering schools
one of the first required courses in our curricu-
lum is a course on material balances. Additional

The usage of multiple-choice
examinations, especially when computer
scoring ... is employed, obviously facilitates
the grading process, in comparison with
conventional problem-based
engineering examinations.

related topics covered in this course include dimen-
sions and units conversion, ideal and real gases,
introductory material on phase equilibria and
numerical methods. This course is normally taken
by our students during the first quarter of their
sophomore year. The text we currently use is that
of Felder and Rousseau [2], and the first seven
chapters are covered. During the past ten years, we
have also employed the texts by Himmelblau [3]
and by Hougen, Watson and Ragatz [4].
A sample of four multiple-choice exercises em-
ployed in recent examinations of this course is pre-
sented in Table I. In the formulation of the alter-
nate incorrect answers to these exercises,
commonly encountered errors are incorporated.
Thus, for example, in the first exercise of Table I,
for which the correct answer is 308 kPa (or B) the
value of 207 kPa (choice A) results when one
fails to add the atmospheric pressure to the gauge
pressure before performing the units conversion.
Similarly, in the third exercise involving the ideal
gas law, for which the correct answer is 219 ft3


SPRING 1981








TABLE 1
Sample of Multiple-Choice Exercises Used
in the Course on Material Balances
The recommended air pressure in the back tires of a
late-model Toyota Celica is 30 psig. Assuming that the at-
mospheric pressure is 14.7 psia, what is the absolute tire
pressure in kilopascals?
A) 207 B) 308 C) 2,310 D) 66,600 E) 308,000
A certain manufacturer of activated charcoal advertises
that one pound of their product has 150 acres of surface
area for adsorption purposes. How many square meters
of surface area are there in one gram of this material
(1 acre = 4840 square yards)?
A) 2.95 B) 34.0 C) 37.2 D) 148.7 E) 1338.
Assuming ideal gas behavior, calculate the number of
cubic feet of carbon dioxide gas at 680F and 2 atm pres-
sure which may be obtained from 50 lbs of dry ice.
A) 1.14 B) 28.2 C) 219. D) 344. E) 438.
An aqueous solution containing 100 grams of dissolved
MgSO4 is fed to a crystallizer wherein 80% of the dis-
solved salt crystallizes out as MgSO,-6HO crystals. How
many grams of the hexahydrate salt crystals are obtained
from the crystallizer?
A) 42.1 B) 80.0 C) 100.0 D) 151.8 E) 189.8


(or C), the incorrect value of 28.2 ft3 (choice B)
results when the temperature in F rather than in
R is employed in the calculations (assuming all
other steps are correctly performed).

UNIT OPERATIONS

ANOTHER COURSE IN WHICH we have used
multiple-choice examinations is the second
course in our three-course sequence on unit opera-
tions. Such stage-wise operations as distillation,
absorption, extraction and leaching are covered in
this course. The text we have used for some years
now is that of McCabe and Smith [5]. Specifically,
Chapters 17 through 21 of that text are covered in
this course.
Obviously, graphical constructions (e.g., Mc-
Cabe-Thiele or Ponchon-Savarit) cannot be easily
incorporated into multiple-choice exercises, al-
though some testing of graphical concepts can be
incorporated. The requirement of complex graphi-
cal constructions, of course, also presents some
difficulties, such as excessive time consumption, in
conventional problem-based examinations.

REACTOR DESIGN

T HE CONCEPTS COVERED by the multiple-choice
exercises used in our reactor design course
include activation energy, half-life, CSTR se-
quences and plug-flow reactors. This course is


... we plan to investigate
the feasibility of computer-aided
generation of such examinations.


normally taken by our students during the second
quarter of their senior year. The text that has
been used for more than 10 years now is that by
Levenspiel [6] (first 8 chapters), although the
text by Cooper and Jeffries [7] was also employed
for a brief period of time a few years ago.

PROCESS CONTROL

SPECIFIC CONCEPTS COVERED by the exercises in
our course on process control consist of con-
troller settings, Routh test, Ziegler-Nichols method
of tuning controllers and frequency response. This
course is normally taken by our students con-
currently with our reactor design course discussed
above. The text currently used in this process
control course is the one by Weber [8] (all chapters
except 11), which superseded earlier usage of
Murrill's text [9].
Examinations based upon multiple-choice
exercises have also been employed in our senior-
level elective course on computer-aided process
design. A detailed description of this elective
course and its contents was presented earlier in
this journal [10].

COMPUTER SCORING
IN THE EARLY STAGES OF usage of multiple-choice
examinations, manual methods were employed
in the grading or scoring of the examinations. This
is a simple enough task, but can become quite time-
consuming in courses or sections thereof with large
numbers of students. Thus, we have recently im-
plemented computer scoring of these multiple-
choice examinations. A brief description of this
capability is given below.
The central computing center at Georgia Tech
is based upon a Control Data Corporation
CYBER 74-28 digital computer. Included in the
support facilities of this center is a 7010 Mark-
Sense Scanner, produced by National Computer
Systems (NCS). This scanner will read forms
(NCS Trans-Optic P099B-25 24 23 22 21) which
have been filled out with a #2-1/2 pencil or softer.
There are five choices (A through E) available for
each question or exercise; a total of 240 such
questions can be accommodated on a single form.


CHEMICAL ENGINEERING EDUCATION








The scanner (an off-line device) assembles all of
the information on the forms and produces a mag-
netic output tape. This tape is then fed to the
central computer. The actual scoring of the
examinations is then performed with a program
known as SGRADER, written in the COBOL
language by Georgia Tech's Office of Computing
Services.
Aside from the forms filled out by the students
and a master key form, the following information
is also supplied in card form to the SGRADER
program:
Department identification and course number
Total number of exercises
Identification of the specific examination
o Numerical identification of the key
Values or weights for each correct answer
Penalties for each incorrect answer
The latter two input items are optional; default
values for the weights and penalties are 1 and 0,
respectively. The capability exists to input


tions have been referred to as brutal, de-
humanizing and criminal, among other descriptive
adjectives. Many of our students become quite
upset when forced to come up with a correct
answer, with no partial credit given. Of course,
the argument for partial credit loses some of its
merit when a sufficiently large number of multiple-
choice exercises is employed in a given examina-
tion.
It has been our experience that using the choice
of "none of the above" in these exercises is a mixed
blessing. Certainly, it is a salvation to the instruc-
tor whenever he has erred and not supplied the
correct answer. On the other hand, with quantita-
tive exercises and particularly if a graph (such as
a compressibility factor chart) has to be read
during the solution process, the usage of "none
of the above" can lead to difficulties associated
with accuracy and judgment. Thus, we generally
try to avoid "none of the above" in the construc-
tion of such exercises.


The reactions of our chemical engineering students to these multiple-choice
examinations can be described, at best, as mixed. These examinations have been referred to as
brutal, dehumanizing and criminal, among other descriptive adjectives.


different weights and/or penalties for the various
exercises.
The output from this program consists of the
following information:
1) Listing of the students in alphabetic order and their
raw scores and scores normalized to 100, plus the
number of correct answers, incorrect answers and
omitted questions (no weight or penalty associated
therewith) for each student.
2) Same information as in 1) above, but ordered by
student scores from high to low.
3) Mean and standard deviation of the examination
results.
4) Breakdown of the student response to each question
(correct, incorrect, omitted).
5) Tabular distribution of the raw scores (individual
and cumulative).
6) Histogram of the scores and frequency thereof.
The entire process of reading the optical forms,
transferring the magnetic tape to the computer,
running the program and printing the output
takes about ten minutes, and is often done while
one (generally a teaching assistant) waits.

STUDENT REACTION

T HE REACTIONS OF OUR chemical engineering
students to these multiple-choice examinations
can be described, at best, as mixed. These examina-


FUTURE PLANS
B ASED UPON 3-4 YEARS OF experience using
multiple-choice examinations as described in
this article, it is clear that such examinations are
a valid and useful testing tool in many of the
standard chemical engineering courses in the
undergraduate curriculum. Accordingly, we plan
to continue using them, and look forward to
further refinements and improvements. Specific-
ally, we plan to investigate the feasibility of
computer-aided generation of such examinations.
This capability has become a distinct possibility
with the recent improvements and developments
in the area of test processing. At least one chemi-
cal engineering school reports the usage of text
processing as an aid to students in the preparation
of laboratory reports [11].
For a specific course, the plan is to create a
large computer file of stored multiple-choice
exercises. The number of such exercises for a given
course should probably be of the order of 500-1000.
These exercises would then be divided in modular
form into the various concepts covered in that
course, e.g., dimensions, units conversion, frac-
tional conversion, recycle, ideal gases, phase rule,
etc. In constructing an examination for this course


SPRING 1981









then, the instructor could scan the contents of this
file, perhaps using a CRT terminal in his office.
He could copy the exercises he wants to use onto a
temporary working file. This file would then be
fed, along with a canned text-processing pro-
gram, to a typewriter terminal (with upper- and
lower-case capabilities, along with subscripts and
superscripts). The original copy of the examina-
tion would then be typed, additional copies made
as required by conventional means, and the work-
ing file could be destroyed. Obviously, there will
be a need to address the security aspects of this
plan. Given a large enough master file of such
exercises, however, security problems would be
minimized. It is conceivable, again given a
sufficiently large number of exercises for a given
course, that the master file could be placed in the
public domain as a study aid to students. Ol

ACKNOWLEDGMENT
The assistance of Professor Mark White in the
preparation of some of the exercises presented
herein and of Mr. Steven Farrow in the proof-
reading of this article is gratefully acknowledged.

REFERENCES
1. Poehlein, G. W., "ChE at Georgia Tech-A Period
of Transition," Chem. Engrg. Education, 2, Winter
1980.
2. Felder, R. M. and Rousseau, R. W., "Elementary
Principles of Chemical Processes," Wiley, New York
(1978).
3. Himmelblau, D. M., "Basic Principles and Calcula-
tions in Chemical Engineering," 3rd Edition, Prentice-
Hall, Englewood Cliffs, N.J. (1974).
4. Hougen, O. A., Watson, K. M. and Ragatz, R. A.,
"Chemical Process Principles. Part I. Material and
Energy Balances," 2nd Edition, Wiley, New York
(1967).
5. McCabe, W. L. and Smith, J. C., "Unit Operations of
Chemical Engineering," 3rd Edition, McGraw-Hill,
New York (1976).
6. Levenspiel, O., "Chemical Reaction Engineering," 2nd
Edition, Wiley, New York (1972).
7. Cooper, A. R. and Jeffreys, G. V., "Chemical Kinetics
and Reactor Design," Prentice-Hall, Englewood
Cliffs, N.J. (1971).
8. Weber, T. W., "An Introduction to Process Dynamics
and Control," Wiley, New York (1973).
9. Murrill, P. W., "Automatic Control of Processes,"
International Textbook Co., Scranton, Pa. (1967).
10. Sommerfeld, J. T., "An Elective Course on Com-
puter-Aided Process Design," Chem. Engrg. Educa-
tion, 126, Summer, 1979.
11. Kirmse, D. W., University of Florida, Private Com-
munication, Oct., 1979.


REVIEW: Polymer Processing
Continued from page 59.
ology). In reality, however, the majority of be-
ginners (for instance, B.S. degree holders in
chemical engineering) do not have adequate back-
grounds in all of these subjects. Therefore those
who wish to write a textbook of polymer process-
ing at the elementary level should make a special
effort to introduce the reader to the background
materials necessary for understanding the basic
principles of polymer processing operations. In
this connection, the authors are to be congratulated
for the commendable job done in putting the very
complex subject into a single volume in an easily
readable form.
The textbook consists of three major parts:
Part I covers the preparatory materials that in-
clude the structure-property relationships in poly-
meric materials, a review of basic equations de-
scribing the fluid flow and heat transfer, and a
brief introduction to rheology; Part II covers the
plasticating extrusion operation that includes the
melting (or softening) of solid polymers, convey-
ing of molten polymers, and the design of plasti-
cating screws; Part III covers the principles in-
volved in various polymer processing operations.
Problems are given at the end of each chapter. The
authors have made an earnest attempt at treating
the subject of polymer processing from the point
of view of unit operations in chemical engineering
and have succeeded in doing it.
I feel that somewhat too much emphasis is put
on the plasticating extrusion operations, occupying
almost one half (over 300 pages) of the book,
which certainly covers the material beyond the
elementary level. While the subject of mixing is
discussed and emphasized, little is discussed about
applications of the knowledge of mixing to polymer
processing operations. It would have been very
instructive if some practical examples were dis-
cussed of the consequence of poor mixing, yield-
ing poor mechanical properties of the product.
Such a discussion would have introduced the reader
to the processing of two-phase systems (e.g.,
polymer blends, polymers with particulates).
As a whole, the textbook is well organized and
well written. I recommend highly that the book
be used either for a technical elective for the
Senior class in chemical engineering, or for the
first level course of Polymer processing for the
graduate program of polymer science and engi-
neering, or of chemical engineering. O


CHEMICAL ENGINEERING EDUCATION








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classroom


A COURSE IN

SPECIAL FUNCTIONS AND APPLICATIONS

THOMAS Z. FAHIDY
University of Waterloo
Waterloo, Ontario Canada N2L 3G1


AT WATERLOO, APPLIED mathematics-oriented
courses are an important constituent of the
undergraduate programme in chemical engineer-
ing. Since the compulsory (called core) courses
cannot possibly cover all subject matters of
interest, a number of electives are open for
students with a particular penchant for applied
mathematics. It is a genuine pleasure to prepare
and teach these elective courses; students who
enroll in them are usually very well motivated,
possess a good command of background mathe-
matics and are willing to learn more than the ab-
solute minimum required to pass.
The course described in this article deals with
special functions and their applications to (mostly
chemical) engineering problems. It is taught
currently at the third year/second semester (3B)
level, although some fourth-year and beginning
graduate students would be found in a typical
class. All students would have taken by this time
a certain sequence of core courses on calculus,
differential equations and linear algebra, and
would be somewhat familiar with some Bessel
functions such as Jo(x), J (x) and perhaps
J1/, (x). They would also have a reasonably good
understanding of certain key relationships in
physical chemistry, fluid flow, and transport pro-
cesses, which can be obtained via special functions,
although they would not have been exposed to de-
tailed derivations and to all important properties
of these special functions. Such a background is
considered adequate for the pursuit of advanced
studies.
Table 1 shows the course structure and rela-
tive lengths of time spent on major topics. The
one-semester course consists of about twenty four
one-hour lectures with periodic tutorials of about
two hours length. There are two one-hour mid-

Copyright ChE Division, ASEE, 1981


Thomas Z. Fahidy received his B.Sc. (1959) and M.Sc. (1961) at
Queen's University (Kingston, Ontario) and Ph.D. (1965) at the
University of Illinois (Champaign-Urbana) in chemical engineering.
He is Professor and Associate Chairman of Graduate Studies in
the Department of Chemical Engineering, University of Waterloo
(Canada) where he teaches courses mostly in applied mathematics
to engineering students and conducts research in electrochemical
engineering. His major research areas are magnetolectrolysis and the
development of novel electrochemical reactors, where he is the
author of numerous scientific articles. Fellow of the Chemical Institute
of Canada and a past associate editor of the Canadian Journal of
Chemical Engineering, he is also a member of a number of pro-
fessional associations and a registered Professional Engineer in the
province of Ontario.


term tests and a three-hour final examination; all
three examinations are open-book-and-notes type
and the use of numerical tables and small com-
puting devices is required. Orthogonal polynomials
and Bessel functions make up approximately one
half of the course inasmuch as these quantities
are particularly important in many applications.
The major objective here is to provide students
with at least an adequate understanding and ap-
preciation of the usefulness of special functions
in the modelling of problems taken from various
areas of engineering and applied physics. The
course emphasizes that special function-oriented
techniques can often be superior time savers with
respect to numerical solutions of certain types of
differential equations, based on the calculus of
finite differences. Apart from instilling factual


CHEMICAL ENGINEERING EDUCATION









knowledge, the course reminds students that
(classical) analytical techniques invariably hold
their place in the sun and that excessive emphasis
on purely numerical methods is often detrimental
to analytical judgment. The course illustrates that
the knowledge of special functions often allows
the solution of a problem literally on the back of
an envelope.
One of the didactic problems facing the instruc-
tor is the proper blend of background theory and
applications. My experience indicates that build-
ing the course material around "model-nuclei"
was very useful in trying to strike the right

TABLE 1
Structure of the Course in Special Functions*


Topic


Gamma and
Beta
Functions


Error- and
related
Functions
Exponential
and
related
integrals


Major Headings and
Illustrative Examples


Appx. Fraction
of time spent
on topic,
per cent


General theory; motion in
force fields; convective
diffusion in a rotating disk
electrode cell; perimeter- and
area- calculations
General theory: quality
control problems; diffusion
and heat conduction
General theory; evaluation
of specific integrals; exploita-
tion of a shallow oil
field; reactor performance
problems


Orthogonal General theory of Legendre
polynomials and Chebyschev polynomials;
steady state potential dis-
tribution problems; numerical
integration (Gaussian
quadratures)


Bessel
functions
and Kelvin
functions


General theory of the J, Y, I
and K functions. Diffusion in
cylindrical porous media;
heat dissipation problems;
variable mass dynamics;
heat transfer in fins; skin
effect in transmitting AC
power


Elliptic General theory; pendulum, 15
integrals and mechanical braking, capillary,
elementary magnetic field generated by
Jacobi elliptic circular current paths.
functions Problems in elliptical
geometry

*One semester course; total number of one-hour lectures is
about twenty-four.


The major objective is to provide ...
an adequate understanding and appreciation
of the usefulness of special functions in the
modeling, of problems taken from various areas
of engineering and applied physics.


balance between theory and applications. To illus-
trate this concept, consider, for instance the
Legendre polynomials, Pn(x); x = cosO. The ex-
pansion


Bn
l(r, 0) = Y (Arn + ) P (cos0)
n=0 r


describes steady state potential distributions in
spherical geometry; the set of indeterminate
constants An and B, depends on the specific
auxiliary conditions of a given physical problem.
Eq. 1 would be typically introduced by discussing
in a class lecture the steady state temperature dis-
tribution in a homogeneous hemisphere whose
surface is maintained at a constant temperature
and whose base (equatorial plane) is insulated.
Starting from the appropriate heat balance
written for the fractional temperature u:

r2urr + 2rur + [sin u,] (2)
sinO aO
(the subscripts denote partial derivatives), Eq. 1
is derived by the classical separation of variables
approach and then it is shown by means of the
auxiliary conditions u (R, 0) = 1; u, (0 = ir/2) =
0 that the specific solution of this problem may be
expressed as


u (r,0) = 2 A, r2n+l)P2(n+l) (cose)
n==O


where

2n+3 ./2
A,- '
R2(n+l) O
0


P2(n+l) (cose) sin0d0


A subsequent homework assignment contains
several problems where the physical systems are
quite different, nevertheless Eq. 1 plays a pivot-
ing role; one such problem would be e.g. the
electrostatic potential distribution around a
conducting sphere placed suddenly into an electric
field of uniform strength of Eo. Since from the
theory of electrostatics, V(r -- oo) = -EorP.
(coso), the solution is obtained as V(r,0) =
R3
-Eor (1 r- )cos0, if R is the radius of the
rs


SPRING 1981









An important aspect of problem
selection is what I would call general
scientific education; i.e. the presentation of
material of historical interest or imaginativeness.

sphere.
An important aspect of problem selection is
what I would call general scientific education; i.e.
the presentation of material of historical interest
or imaginativeness. One of my favourites is Lord
Kelvin's estimation of the age of the Earth in the
last century, well before the advent of big-bang
theory (I owe this problem with thanks to Pro-
fessor Jim Westwater's graduate course in heat
transfer at the University of Illinois). In 1897
Kelvin used the following model for the stated
computation. The Earth was a liquid sphere until
time zero when solidification of the crust began.
The temperature in the centre of the Earth is
To = 7000F, the average temperature on its
surface is T. = 50F; the geothermic gradient at
the surface is -10F per 50 ft. Finally, the average
thermal diffusivity of the crust is a = 0.0456 ft2/h.
The model is related to the error function, and if
T is the temperature at radial position r, then if
x = R-r,


function), chemical reactor performance (ex-
ponential integral), concentration distribution
near the surface of a rotating disk electrode
(gamma functions and incomplete gamma
functions), heat transfer in a non-homogeneous
bar (Legendre polynomials), heat transfer from
fins (Bessel functions), capillary between parallel
plates (elliptic integrals) and a number of others.
To illustrate one such problem, consider the con-
secutive reaction scheme A-*kiB--kC where the
first decomposition is second order and the second
decomposition is first order. If we set the initial
concentration of species A to Ao, and if there are
no B and C moles present at zero time, the mass
balance equations


dB
= k,A: k2B

dA -
dt
with initial conditions A(o) =
C (o) = 0 fully define the reaction
is solved immediately as
A= A
S1 + Aokt
and upon substitution into Eq. 7
Laplace transformation we obtain


(7)

(8)

Ao, B(o) =
system. Eq. 8


(9)
and applying


T-T, x
s erf -x=
To Ts 2 at
and it follows that


dT
dx I=-


S
1/k, Aok,
B(s)- 1k [Ao + R, + se AkEi ( )]
s + k, Aok,
(10)
where


T T,.
Vwrat


Thus we calculate t 107 years; accepting the
much more probable value of about 4.6 x 109 years
from the study of fragments of moon rocks, we
cannot help marvelling at the relative closeness
of Kelvin's result in spite of the gross simplifica-
tions carried with it; after all, two orders of
magnitude in astronomy is "peanuts", and Lord
Kelvin did not even possess an LCD programmable
calculator, to boot! It is even more intriguing to
estimate the temperature of the Earth 100 miles
below the surface: from Eq. 5, and neglecting the
slight difference between 1979 and 1897 we obtain
about 6,600F. This is only about 6%o off the core
temperature.
Problems of closer chemical engineering
interest, whose solution may be obtained in terms
of special functions, include unsteady-state diffu-
sion of pollutants (error function), heat loss
through metal fastenings of insulators (error


et
Ei(x) =3 -t dt
-00


(11)


is the exponential integral. Eq. 10 may be inverted
by means of the convolution theorem, which
yields


t e_2(t-_u)du
B (t) = 1 + u ) 2
0 \Ao k k


Upon integration and some algebraic manipula-
tion, this gives
A0
B(t) = Aoet A -
A,klt + 1
1
k, (t + A )k k,
e Ak1 [Ei(k2t + Ak
k, )


-Ei( )]
AO-k91


(13)


CHEMICAL ENGINEERING EDUCATION


(12)


















lim B (t) = 0
t--oo


If, for instance, Ao = 1 mol/L; ki = 0.5 L/mol*
min, k, = 1.0 min-1, then Bmax s 0.199 mol/L and
the corresponding tmax s 1.2 min.
The wealth of Bessel-function oriented
problems is given a somewhat condensed yet
representative treatment, as seen in Table 1; about
one fourth of the course is devoted to Bessel
functions. Here one typical problem discussed is
the cooling of a cast metal tube in still air, when
axial conduction may be neglected. The unsteady
state heat balance


with
-k


3T T( a 1 T (14)
at ?r2 +r ar
auxiliary conditions T(o,r) = To and
T I = h(T T,), (Ta is the constant
or R


ambient temperature), is solved to

at
T-T 02 0e R2
T T 2 = e
To Ta n=1


J (x)
x,[Jo2(xn) + J12i(Xn)]


Jo(Xn r
R


where the eigenvalue set (x,) is obtained via Eq.
16:
Jo(xn) kx,.
J -(x1) (16)
J (xn ) hR
In the case of metals of good conduction proper-
ties, a useful short-cut reduces numerical work
drastically, if R is relatively small: because of the
relative largeness of the k/hR group, x, will be
substantially less than unity, hence Jo(x) /J, (xx)
will tend to 2/x, and a very close approximation
to the first eigenvalue is xx 2hR Moreover,
k
since x2 >> x, Eq. 15 may be safely truncated
after the first term. Taking e.g. a 5 cm diameter


The course described in this article
deals with special functions and their applications to
(mostly chemical) engineering problems.


The existence of a maximum concentration of the
intermediate in the reaction scheme may be quickly
demonstrated, by looking at limiting values:


SPRING 1981


lim B (t) = 0
t-0-


zirconium tube and To = 900C, Ta = 30C, then
with the physical data: c, = 320 J/kg-K, p t=
6500 kg/m3, h = 26 W/m2*K, k = 24W/m-K, a
good approximation is obtained by using the short-
cut estimate of x,1 0.233 in Eq. 17 (t is in hours,
r in metres) :
T 30 + 1176.15 e-3-6"8tJ (9.32r) C (17)
By trial and error, the first root of Eq. 16 is found
to be slightly larger than 0.24, thus the short-cut
approach is quite acceptable. Note that x, r 3.84
and, in consequence, the corresponding exponential
term in Eq. 15 will be small enough at times not
too close to zero to justify the omission of the
second and higher order terms in the expansion.
This problem is a good illustration of the superi-
ority of the analytical approach employed to a
finite-difference based numerical solution of Eq.
14, as far as time and effort is concerned.
A somewhat vexing problem associated with
the course is the selection of a particular text-
book. The text of Lebedev [1], while well written
and comprehensive in orthogonal polynomials,
spherical harmonics and hypergeometric functions,
is light on gamma-and related functions, and on
the application of exponential-and related inte-
grals; elliptic integral are not treated at all.
Moreover, the somewhat restricted number of
examples do not reach into the depth of the
variety of engineering-oriented problems and
students find this aspect rather frustrating.
Nevertheless the text can be used with caution as
background material for the theoretical frame-
work of the course and a large proportion of the
lectures can thus be devoted to solving practical
problems. In this respect the excellent book by
Reddick and Miller [2], now unfortunately out of
print, served as references for the lecture notes
and for numerous homework problems; to a lesser
extent, Arfken's [5] sections on gamma functions,
Legendre functions and Chebyschev polynomials
were found useful. The chapter in Mickley et al.
[6] on Bessel functions is one of the best of its
kind. In treating computational aspects, the hand-
book of Abramowitz and Stegun [3] and the al-
gorithmic tabulations of Smith [4] are more than
adequate. By contrast, texts under the generic
title of "advanced engineering mathematics" are
in my view rather disappointing, with the possible
exception of Kreyszig [6]. Some Dover paperbacks
serve as excellent references for certain topics e.g.
Bowman [8], Relton [9], Farrel and Ross [10] and
Sneddon [11] in the area of applied Bessel








functions.
The students' response to the course has been
quite positive. They appreciate the relevance of
the topics covered to other chemical engineering
courses, especially in solving homework problems
which facilitate a deeper understanding of the
mathematics pertaining to heat- and mass trans-
fer, chemical reaction engineering and other com-
ponents of our discipline. In courses where these
subject matters are taught, there is usually in-
sufficient time for an instructor to go into the
depth of the mathematical treatment (even if he is
inclined to do that at all) and mathematical back-
ground receives superficial attention. The course
on special functions reduces this gap at least for
those students who are interested in obtaining a
better mathematical education than what is
normally available in core courses.
Finally as a developer and instructor of this
course, I enjoy it immensely not only for the
pleasure of a mature and motivated audience but
also for having learned a great deal about the im-
pressive richness of XVIIIth and XIXth century
mathematics, whose full potential, I believe, has
not yet been fully discovered. Apart from its use-


fulness, it offers much intellectual beauty for
chemical engineering educators who see more in
mathematics than a mere tool for solving
problems. E

REFERENCES
1. N. N. Lebedev, Special Functions and Their Applica-
tions, Dover (1972).
2. H. W. Reddick and F. H. Miller, Advanced Mathe-
matics for Engineers, Wiley (1956).
3. M. Abramowitz and I. A. Stegun (eds), Handbook of
Mathematical Functions etc. . Dover (1965).
4. Jon M. Smith, Scientific Analysis on the Pocket Calcu-
lator, Wiley (1975).
5. G. Arfken, Mathematical Methods for Physicists 2nd
ed. Academic Press (1970).
6. H. S. Mickley, T. K. Sherwood and C. E. Reed, Applied
Mathematics in Chemical Engineering, McGraw-Hill
(1957).
7. E. Kreyszig, Advanced Engineering Mathematics 4th
ed., Wiley (1979).
8. F. Bowman, Introduction to Bessel Functions, Dover
(1958).
9. F. E. Relton, Applied Bessel Functions, Dover (1965).
10. 0. J. Farrell and B. Ross, Solved Problems in
Analysis, Dover (1971).
11. I. N. Sneddon, Special Functions of Mathematical
Physics and Chemistry, Oliver and Boyd (1961).


division activities


SUMMER SCHOOL '82

T. W. F. RUSSELL
University of Delaware
Wilmington, DE 19808

The next Summer School for Chemical Engi-
neering Faculty, sponsored and organized by the
Chemical Engineering Division of the ASEE, will
be held August 1-6, 1982, at the University of
California at Santa Barbara. Prof. Dale E. Seborg,
Chairman of Chemical & Nuclear Engineering,
will be handling the local arrangements.
The 1982 Summer School will expand upon the
theme that chemical engineers need to have an
impact on society in a broader sense. Sessions
are planned to discuss means of making students
aware of their potential role in issues such as
public policy, the environment, and energy policy.
A poster session devoted to new course and cur-
ricula development is planned, as well as a set of
sessions devoted to those technical subjects which


will become of key importance in the next decade.
The subjects of the workshops are not yet fixed.
We are still receiving input from chemical engi-
neering faculty regarding subjects which would
match well with the evolving needs of industry and
our society.
In August 1980 proposals requesting donations
to support the 1982 Summer School were mailed

TABLE A
Donations Received or Pledged
(as of March 1, 1981)
BASF Wyandotte Corporation
Celanese Corporation
Dow Chemical U.S.A.
E. I. du Pont de Nemours & Company, Inc.
Eastman Kodak Company
Exxon Research & Engineering Company
General Mills Foundation
Merck, Sharp & Dohme Research Laboratories
The NL Industries Foundation, Inc.
Olin Corporation Charitable Trust
PPG Industries Foundation
Rohm & Haas Company
Shell Development Company
Stauffer Chemical Company
Union Carbide Corporation
Weyerhaeuser Company Foundation


CHEMICAL ENGINEERING EDUCATION







to 117 companies and foundations. In March of
1981 proposals were mailed to an additional 14
foundations. The total support required is esti-
mated to be $123,000. At the present time, 53
companies have responded and 19 have pledged
or contributed approximately $73,000. The
Organizing Committee is particularly anxious to
know of additional firms or foundations who may
have an interest in supporting this educational
program. If you have any suggestions concerning
key contacts, please call T. W. F. Russell (302)
995-7155 to discuss how these individuals and
their organizations should be contacted.
The estimated budget accounts for preliminary
operating expenses; travel and living expenses
for members of the Organizing Committee, work-
ship coordinators and leaders; special events; and
partial travel and living subsidy for university
participants. There is no compensation for instruc-
tional services. Members of the Organizing, co-
ordinators and leaders of workshops, as well as
their institutions, donate their services.
Each department of chemical engineering will
be offered partial subsidy for one faculty member
to attend the Summer School. Large departments
will be offered an opportunity for a second faculty
member to participate. Department heads will be
asked to name attendees from their department.
Industrial sponsors will also be invited to select
one or two attendees from their company.
For more information or copies of the 1982
Summer School for Chemical Engineering Faculty
Proposal to Industry, please contact T. W. F.
Russell, Co-Chairman Institute of Energy Con-
version University of Delaware One Pike Creek
Center Wilmington, DE 19808.


book reviews

LIQUIDS AND THEIR PROPERTIES:
A MOLECULAR AND MACROSCOPIC
TREATISE WITH APPLICATIONS

By H. N. V. Temperley and D. H. Trevena
John Wiley & Sons, New York, 1978

Reviewed by Keith E. Gubbins
Cornell University
This book gives an elementary account of both
the molecular and macroscopic approaches to
liquids, and will be most useful to nonspecialists


who want an overview of the subject. The authors
do not assume any significant prior knowledge of
statistical mechanics or fluid mechanics, and the
book is interesting and easy to read.
The first chapter gives a historical survey, and
includes photographs of Kirkwood, van der Waals,
Bernoulli and Berthelot. This is followed by three
chapters on the intermolecular forces and statisti-
cal mechanical theories of liquids. A brief account
of each theoretical approach is given, stressing
the physical ideas without giving detailed deriva-
tions. The chapters which follow focus on particu-
lar applications, and are the most interesting and
unusual feature of the book. They include discus-
sions of phase transitions, hydrodynamics,
acoustics, surface waves, ultrasonic waves,
liquids under tension and compression, surface
phenomena, liquid structure, mixtures, transport
processes, non-Newtonian liquids, and liquid
helium. The treatment of these subjects is at an
elementary and largely qualitative level. In
Chapter 8 the authors adopt the novel approach of
dealing at length with liquids under negative pres-
sure (i.e. tension) before discussing the effects of
positive pressure! The authors' research has
contributed to our knowledge of liquids under
tension, and it is because of Berthelot's early ex-
periments on this subject that his photograph is
included in the historical chapter.
While valuable as an introduction for non-
specialists, this book is less suitable to those read-
ers interested in a deeper treatment. Many topics
are introduced in a rather cursory way and equa-
tions are presented without detailed proofs. The
theories given are not always up-to-date. Thus, no
mention is made of either perturbation theory or
the more modern versions of conformal solution
theory (e.g. van der Waals 1 theory) and integral
equation theory. The chapter on mixtures deals
almost entirely with the cell model approach, now
largely abandoned by theorists in favor of the more
powerful conformal solution and perturbation
theory methods. The book is reasonably free from
errors, although I did note a few. Thus one cannot
study either the mean kinetic energy or nonequi-
librium processes by the Monte Carlo method (p.
195), and the treatment of electrostatic forces in
terms of angle averaged models is an oversimpli-
fication for most polar liquids. Nevertheless, these
flaws are relatively minor, and many chemical
engineers will appreciate the inclusion of such
topics as hydrodynamics, non-Newtonian fluids,
and cavitation. O


SPRING 1981









CRYOGENIC HEAT TRANSFER
Continued from page 72.
Flows in both tube and shell side of coiled tube
exchangers are generally turbulent. Pressure
drops for single-phase tube side flows can be
calculated using the normal Fanning friction
factor correlation for straight tubes and then
applying an empirical correction factor to take
care of the effect due to the radius of curvature of
the tubing. Shell-side pressure drops for single-
phase flow can be estimated using the correlations
of Grimison [7]. Again, corrections need to be
applied to account for the effect of spacers, angles
of the tubes, and other mechanical configurations.
Accuracies in many of the two-phase pressure
drop correlations still leave much to be desired.
The correlation of Chenoweth and Martin [8] still
appears to provide the most satisfactory pressure
drop prediction in the cryogenic region for tube-
side two-phase flow. However, even this correla-
tion provides design data with an uncertainty of
25%. The pressure drop correlations for shell-
side two-phase flow offer about the same difficul-
ties.
The largest coiled-tube exchangers contained
in one shell have been constructed for LNG base
load service. These exchangers handle liquefaction
rates in excess of 100,000 nm3/h with a heat
transfer surface of 25,000 m2, an overall length
of 61 m, a maximum diameter of 4.5 m, and a
weight of 200 tons. Length of the tubes in one of
these exchangers exceeds 5.4 x 106 m (3400 miles).

Plate-Fin Exchangers
Heat exchangers of this type consist of heat ex-
change surfaces obtained by stacking alternate


FIGURE 5. Exploded view of one layer of plate-fin ex-
changer before brazing.


HOT FLOW

--
______ COLD FLOW

u -^-- ---*=


FIGURE 6. Two heat exchanger geometries designed
to minimize uneven flow distribution.
layers of corrugated, high-uniformity, die-formed
aluminum sheets (fins) between flat aluminum
separator plates to form individual flow passages.
Each layer is closed at the edge with solid alumi-
num bars of appropriate shape and size. Figure 5
illustrates by exploded view the elements of one
layer, in relative position, before being joined by
a brazing operation to yield an integral rigid
structure with a series of fluid flow passages. The
latter normally have integral welded headers.
Several sections may be connected together to
form one large exchanger. The main advantages of
this type of exchanger are that it is (1) compact
(about nine times as much surface area per unit
volume as conventional shell and tube exchangers),
yet permits wide design flexibility, (2) involves
minimum weight, and (3) allows design pressures
to 60 atm from 4 to 350 K.
Variations in flow through the many passages
is also a problem with plate-fin exchangers. In
miniature plate-fin exchangers the problem can
be minimized with a novel approach outlined by
Cowans [9]. In his solution the geometry of the
hot and cold flow is designed so that a shift in
temperature in the middle of the exchanger affects
only the flow impedance of the hot fluid. Two
possible geometries are shown in Fig. 6. Both
operate to increase the impedance to flow of the
hot fluid as the temperature increases, thereby
reducing the flow rate. A corresponding decline
in impedance with temperature, on the other hand,
results in an increase in the flow rate.
Axial heat conduction along the exchanger
passage walls is another factor that is of con-
siderable importance in the design of plate-fin ex-
changers. The effect of axial heating is illustrated
in Fig. 7 showing idealized temperature distribu-


CHEMICAL ENGINEERING EDUCATION








tion of fluids in such an exchanger. The broken
lines refer to the situation where axial heat
conduction is ignored and the solid lines depict
the modified temperature distribution when axial
heat conduction is included. In high performance
heat exchangers, the fluid temperature difference
is already quite small. Decrease of the idealized
temperature difference due to axial conduction
contributes to a further deterioration of exchanger
effectiveness. The effect is particularly severe in
plate-fin exchangers with short flow passages that
are designed to operate with large temperature
differences between the inlet and outlet tempera-
tures to the exchanger. The mathematical relation-
ships are relatively complex and Kroeger [10] has
provided useful design charts for both balanced
and unbalanced flow in plate-fin exchangers.
Various flow patterns of brazed plate-fin ex-
changers can be developed to provide multipass or
multistream arrangements by incorporating suit-
able internal seals, distributors, and external head-
ers. In the simple cross-flow layout the corruga-
tions extend throughout the full length of each set
of passages with no internal distributors. Such an
arrangement is suitable when the effective mean
temperature difference obtained in cross-flow is
-C,91
-c,,e,
1.0. C82 --
'C^' /WITHOUT AXIAL CONDUCTION
ITH AXIAL CONDUCTION










FIGURE 7. Effect of axial conduction on temperature
profile in exchanger.

not too far below the logarithmic mean tempera-
ture difference calculated for countercurrent flow.
This is a condition that is encountered in liquefiers
where there is little change in temperature on the
condensing side and the large flow of low-pressure
gas on the warming side requires a large cross
section and short passage length. The multipass
cross-flow arrangement can be considered as
comprising several cross-flow sections, assembled
in counter-formation, to provide effective mean


temperature difference approaches that more
closely approximate those obtained with counter-
current operation. Construction of this type is
often used for gas-gas and gas-liquid applications.
Countercurrent construction is normally selected
when very high thermal efficiencies (95 to 98 per-
cent) of heat exchange are required.
Design of the brazed aluminum plate-fin ex-
changer resolves itself into selecting a geometry
and surface arrangement to provide a product UA
of the right magnitude. The overall UA of a plate-
fin exchanger can be related to the individual hA
values for the individual component fluid streams
by
UA = [S (hA)h S (hA)e]/[S(hA)h + s(hA)c]
(3)
where the subscripts h and c refer to the warm
and cold streams, respectively.
For single-phase flow the heat transfer co-
efficient is generally expressed in terms of the
Colburn correlation where the numerical coefficient
separates the effects of the fluid properties on
the heat transfer coefficient and permits correla-
tion as a function of the Reynolds number. Because
of the many varied shapes for the fins, it is usually
necessary to test each configuration individually
to determine both the heat transfer and frictional
characteristics for a specific surface. Such in-
formation, in the form of curves relating the
numerical coefficient as a function of the Reynolds
number, is generally available from the heat ex-
changer manufacturers of the various surface con-
figurations.
Information on two-phase heat transfer co-
efficients in plate-fin heat exchangers is essentially
nonexistent and no general correlations are avail-
able for the prediction of these coefficients. In view
of this deficiency, coefficients for condensing, boil-
ing, and multicomponent systems are approxi-
mated using predictions commonly adopted for
single tubes. For example, the relations developed
for two-phase condensing flow in tubes have been
used with reasonable success to determine heat
transfer coefficients under similar operating condi-
tions in individual channels of plate-fin exchang-
ers.
Pressure drops for single-phase flow are
normally expressed in terms of a friction factor.
Values of the latter are conveniently plotted as a
function of the Reynolds number and are obtain-
able from the manufacturers for their various fin
geometries. Proprietary methods for determin-


SPRING 1981








ing the pressure drop in the inlet and exit nozzles,
distributors, and headers are also obtainable from
the manufacturers.
Pressure drop data for two-phase flow are just
as scarce as data for the heat transfer coefficients.
Consequently, the pressure drop is usually as-
sumed to be equal to that produced for all-gas
flow. Modifications to this approach generally
involve using the correlations of Chenoweth and
Martin [8] or Lockhart and Martinelli [11] which
were developed for two-phase flow in tubes.
Plate-fin exchangers can be supplied as single
units or as manifolded assemblies which consist
of multiple units connected together in parallel or
in series. Sizes of single units are presently limited
by manufacturing capabilities and assembly toler-
ances to maximum lengths of 7.3 m and square
cross sections of 1.2 m. The compact design of
brazed aluminum plate-fin exchangers makes it
possible to furnish heat transfer areas in excess
of 35,000 m2 in one manifolded assembly.

Reversing Exchangers
Continuous operation of low-temperature pro-
cesses requires that impurities in feed streams be
removed almost completely prior to cooling the
streams to very low temperatures to avoid opera-
tional difficulties or potential hazards. Thus, there
is an advantage in carrying out the necessary puri-
fication steps in the heat exchangers themselves.
One method for accomplishing this is by using re-
versing heat exchangers.
A typical arrangement of a reversing ex-
changer for an air separation plant is shown in
Fig. 8. Channels A and B constitute the two main
reversing streams. Operation of such an exchanger
is characterized by the cyclical changeover of one
of these streams from one channel to the other.
The reversal normally is accomplished by pneu-
matically operated valves on the warm end and by
check valves on the cold end of the exchanger.
The warm-end valves are actuated by a timing
device which is set to a period such that the pres-
sure drop in the feed channel is prevented from
increasing beyond a certain value because of the
accumulation of impurities. Feed enters the warm
end of the exchanger and as it is progressively
cooled, impurities are deposited on the cold surface
of the exchanger. When the flows are reversed, the
waste stream reevaporates the deposited impuri-
ties and removes them from the system.
Proper functioning of the reversing exchanger


%2 TO WASTE
FIGURE 8. Typical flow arrangement for a reversing
exchanger in air separation plant.
will depend on the relationship between the pres-
sures and temperatures of the two streams. Since
pressures are normally fixed by other considera-
tions, the purification function of the exchanger
is usually controlled by the proper selection of
temperature differences throughout the exchanger.
These differences must be such that at every point
in the exchanger where reevaporation takes place,
the vapor pressure of the impurity must be greater
than the partial pressure of the impurity in the
scavenging stream. Thus, a set of critical values
for the temperature differences exists depending
on the pressures and temperatures of the two
streams. Since ideal equilibrium concentrations
can never be attained in an exchanger of finite
length, allowances must be made for an exit con-
centration in the scavenging stream well below
the equilibrium one. Generally a value close to 85
percent of equilibrium is chosen.
The design of a multistream exchanger is
necessarily more complicated when two of the
streams are subject to flow reversals. The problem
is simplified somewhat by inherent characteristics
of the reversing exchanger. There is always one
warm stream exchanging heat with several cold
streams. In general, a multistream heat exchanger
is sized by applying first-law balances around an
element of the exchanger. A simplified approxi-
mate solution to these energy balances can be made


CHEMICAL ENGINEERING EDUCATION









by assuming a uniform wall temperature for each
differential section. The resulting solution is of
the form
[mC, (Tin Tout)] h = (UA)avATe (4)
where (UA) a is given by


(UA)av = -

IT


n=n
1/ 2 hAn + [1/hhAl]
n = 1 _


and ATe is best defined as
(Tin)h
1 1 C dTh (6)
AT, (Ti Tout)hJ Th- Tn
(Tout) h
Here the subscript h refers to the warm stream
and the subscript n refers to any number of cold
streams.
Estimates for heat transfer and pressure drop
are dependent upon the type of exchanger
geometry used. Exchangers used as reversing ones
in typical air separation plants are subject to ap-
proximately one million pressure reversals over a
fifteen- to twenty-year service life. This severe
duty reduces the maximum allowable pressure with
brazed aluminum exchangers to a value of 10 to
11 atm. Higher-pressure systems can usually be
handled by concentric heat exchangers or paired
tube assemblies in shell and tube exchangers.

Regenerators
Another method for the simultaneous cooling
and purification of gases in low-temperature pro-
cesses is based on the use of regenerators first
suggested by Frankl nearly sixty years ago.
Whereas in the reversing exchanger the flows of
the two fluids are continuous and counter current
during any one period, the regenerator operates
periodically storing heat in a matrix in one-half
of the cycle and then giving up the stored heat to
the fluid in the other half of the cycle. Such an
exchanger consists of two identical columns packed
with a solid high-heat capacity material such as
metal ribbon, or stones, through which the gases
that are to be cooled or warmed flow.
In the process of cooldown the warm feed
stream deposits impurities on the cold surface of
the matrix. When the streams are switched, the
impurities are reevaporated in the cold gas stream
while simultaneously cooling the matrix. Thus, the
purifying action of the regenerator is based on the


same principles as presented earlier for the revers-
ing exchanger and the same limiting critical
temperature differences need to be observed if com-
plete reevaporation of the impurities is to take
place.
The low cost of the heat transfer surface, the
large surface area per unit volume of matrix, and
the low pressure drop are the principal advantages
of the regenerator. However, the intercontamina-
tion of fluid streams by mixing due to periodic flow
reversals and the difficulty of regenerator design
to handle three or more fluids has restricted their
use and favored the adoption of brazed aluminum
exchangers.
Because of the time dependence of the tempera-
tures in a regenerator, its analysis is more complex
than that of a heat exchanger. Application of the
first law to an element of regenerator length pro-
vides differential equations describing the heat
transfer processes associated with the gas and the
matrix. With the simplifying assumption of negli-
gible conductivity of the matrix parallel to the
direction of gas flow, such equations can be com-
bined to provide a partial differential equation for
the temperature of the gas flowing through the re-
generator as a function of the number of heat
transfer units, a dimensionless length coordinate,
a dimensionless time coordinate, a switching
period, and a temperature ratio for the cooling
and warming period:
D 2T hA T hA ~TT
+ + _P
(7)
where h is the overall heat transfer coefficient
between the gas and the packing, A is the total
area, L is the length of packing, m is the mass of
packing, T is the time, and the subscripts p and g
refer to the matrix material and gas, respectively.
A classic numerical solution of this expression for
the case of steady-state cyclic operation of a re-
generator has been made by Hausen [12].
Knowledge of the temperature distribution then
permits calculation of the actual energy trans-
ferred from
1/f L
Qact = h(A/L) (T,-T) dLdr(8)
0 0
where f is the frequency of the heating or cooling
cycle. Similar analytical solutions to these two
equations involving various simplifying assump-


SPRING 1981









tions have been developed by a number of investi-
gators and have been summarized by McDonald
[13].
Regenerators quite frequently are chosen for
applications where the heat transfer effectiveness
must approach values of 0.98 to 0.99. To attain
such a high regenerator effectiveness requires a
high heat capacity per unit volume and a large
surface area per unit volume.
Another variable that must be recognized is
the effect of condensibles in the feed gas. For
example, an air separation plant processing a 5-
atm, 20C feed saturated with water vapor will
require an increase in regenerator length of 20
percent over that required to handle a dry gas
feed. Since switchover losses in regenerators can
approach 3 percent of the feed, the optimum re-
generator volume must be determined by an
economic analysis involving volume of unit,
switching time and capital cost of shell plus pack-
ing.
As with all other low-temperature exchangers,
there are certain precautions that must be ob-
served in designing regenerators which are in
addition to those required to obtain the required
heat transfer and thermal capacity characteristics.
For example, the thermal conductivity of the
matrix material in the direction of the gas flow
should be small; otherwise the effectiveness of the
regenerator can be reduced. Generally this can be
remedied by selecting material that is dis-
continuous and using low thermal-conductivity
material for the shell of the regenerator.

TRANSIENT HEAT TRANSFER CONSIDERATIONS

T HE MOVEMENT AND STORAGE of cryogenic fluids
always involves transient heat transfer during
the cool-down phase of associated lines and stor-
age tanks. Such equipment is a key component in
a liquefied natural gas (LNG) system for both
base load and peak-shaving plants. The more
common type of storage tank for such LNG
systems is the above-ground double metal-wall
tank. The inner wall of such a storage tank is con-
structed of a steel or aluminum alloy exhibiting
acceptable properties at low temperatures, while
the outer wall is generally constructed of mild
carbon steel. Since such mild carbon steels be-
come brittle below -50 to -100 C and frost-heaving
can occur if the soil below the tank freezes, a po-
tential hazard to the tank is created if cold
temperatures progress too far from the inner tank.


Therefore, the overall insulation scheme and
heater design below such tanks are extremely im-
portant. Failure of the outer tank wall not only
reduces the general tank support, but also results
in methane leakage with its related safety hazard
since the insulated space between the walls, floor
and roof of the tank is normally saturated with
methane gas.
Design optimization of an above-ground double
metal-wall storage tank includes many factors. The
more important factors are: (1) insulation
material and thickness, (2) location and spacing
of the heaters below the tank, (3) heat input to
the heaters, (4) location of the heater tempera-
ture control points, (5) minimization of heat leak
to the tank, and (6) power failure back-up energy
systems. These factors must be considered simul-
taneously to minimize material cost and heat leak
to the tank while preventing the possibility of
failures due to low temperature embrittlement of
the outer tank wall and frost-heaving underneath
the tank.
To aid in the analysis of these many design
factors, a generalized computer simulation of the
transient two-dimensional heat transfer occurring
underneath such a tank was recently developed by
Seeland [14]. The program simulates temperature
profiles below and around the tank as a function
of time. Generalization of the program was under-
taken to facilitate the theoretical analysis of
numerous design options in a relatively short time.

Mathematical Model
The development of a computer simulation for
the transient two-dimensional heat transfer oc-
curring underneath a cryogenic tank during cool-
down must recognize numerous factors. For
example, several different materials will generally
be involved; often with quite complicated geo-
metries. Heat input sources are involved and these
are controlled and energized in a variety of ways.
The mathematical simulation model must be able
to handle both insulated or constant temperature
boundaries depending upon the situation at hand.
The equations for such a transient two-dimen-
sional conductive heat transfer simulation can be
developed from a general energy balance equation
presented by Bird et al [15]. Using Fourier's law
of heat conduction (q = -kVT) and assuming
that the thermal conductivity of the material is
constant, the general energy balance can be ex-
panded in terms of rectangular coordinates to


CHEMICAL ENGINEERING EDUCATION









-3 T 2T + -T
pC T k T + k + Q (9)
-a 0 x2-

and served as the basis for the numerical ap-
proximations in this simulation. Although the
steady-state form of this equation can be solved
analytically, the transient form realistically re-
quires the use of a computer. The finite difference
method which estimates the differential equations
with numerical approximations was selected to
solve equation (9) and establish a grid of points
in the area of the solution. The numerical ap-
proximations themselves are based on changing
the differential variables to discrete variables.
The exact relation to calculate temperature Tj+i
located at x + Ax relative to temperature Tj
located at x in such a transient heat conduction
simulation is given by a Taylor series. The latter
can be rearranged to obtain the first derivative
(aT/ax)j and this can be used to obtain the
second derivative (a2T/ax2) j. Similar equations
can be developed for (a)T/ay2)j and (3T/0D).
With the aid of these relationships, equation (9)
can be reformulated in such a manner that the
temperatures on the right-hand side of the result-
ing equation can be either at the previous time
interval n (explicit) or the new time interval
n + 1 (implicit). The new time interval can then
be calculated upon rearranging the explicit form
of the temperatures in this latter relationship.
Unfortunately, explicit solutions have restric-
tions. In order to assume convergence to the
differential equation solution as Ax, Ay, and AO
are decreased, the ratios of A0/Ax2 and AO/Ay2
are limited in magnitude. Additionally, even
though AO could be increased as steady-state is ap-
proached, the convergence criteria as detailed by
Carnahan et al [16] may limit the size of A0.
The implicit form, on the other hand, results
in an equation with five unknowns. Its use results
in the need to solve a large matrix for the tempera-
tures at all points for the new time interval. In
order to establish smaller matrices for solution,
an implicit method, the alternating-direction im-
plicit (ADI) method [16], was finally chosen for
the simulation calculation. Since the ADI method
is unconditionally stable, it requires no conver-
gence criteria.
The ADI method uses two different finite
difference solutions for each time interval. An
intermediate time interval of (0 + A0/2) is used
to determine intermediate temperatures of T*.


These intermediate temperatures are then used to
solve for temperatures at time (0 + AO).
The first finite difference equation is developed
(explicitly in the x direction and implicitly in the
y direction) and involves only three unknowns.
This permits establishment of a tridiagonal matrix
for each column of temperatures (i.e., for each j,
a matrix is set up to solve for T* at all i's). Solu-
tion of the resulting matrix uses Gaussian elimina-
tion (i.e., the Thomas algorithm).
The computer simulation was originally used
to predict the time-temperature relation at various
specific locations underneath a well-insulated cryo-
genic tank supplied with a heat coil controlled
from one of these locations. Figure 9 presents a
time-temperature profile for three of these loca-
tions. One of the locations was near the center of
the tank at some distance from the heating coil.
The second location was adjacent to the heating
coil and was used as the control point for the
heater. The heater was energized when the
temperature at the location decreased to 5C and
was programmed for shut-off when the tempera-
ture at the location reached 15C. The third loca-
tion was near the edge of the tank but also at
some distance from the heating coil.
A study of the three selected time-temperature
curves indicates that in the first 900 hours of cool-
down the heater was not energized because the


ours
FIGURE 9. Temperature vs. time at three specific loca-
tions underneath a well-insulated cryogenic
tank supplied with heating coils. Legend: 1-
location near center of tank but at some
distance from heating coil; 2-location ad-
jacent to heating coil; 3-location near edge
of tank but at some distance from heating
coil.


SPRING 1981









control point temperature was above 5C during
that time period. Once this specific temperature
was attained, the heater was energized for ap-
proximately 300 hours with a resultant increase
in temperature at this location to 15C. The heater
was then deenergized and the cooling process re-
peated until the temperature had again dropped
at 5C, whereupon the entire process was re-
peated. The effect of the periodic heater operation
at the other locations which were some distance
from the heater was observable but was also
fairly well damped out.
At the end of 3000 hours of operation, the
heater was completely shut off to simulate a power
failure. Since there was no periodic energy make-
up by the heater, the temperatures at all three loca-
tions showed continued decreases in temperature
for the next 1000 hours of monitoring. At the end
of this time it was evident from the time-tempera-
ture record of all three locations that steady-state
still had not been attained. This is not surprising
since 1000 hours (- 40 days) is still a relatively
short time in the cooldown history of many cryo-
genic storage tanks.
More recently the computer program has been
utilized to follow the time-temperature history for
an existing large LNG storage tank. It has been
quite successful in this simulation in duplicating
temperatures observed at numerous locations over
extended time periods and under varying heater
inputs. Differences between observed and pre-
dicted temperatures have been on the order of
1 to 2C. The principal disadvantage to the pro-
gram has been its rather rigid grid structure
which provides some difficulty in establishing
temperature profiles along each material interface
encountered underneath a typical cryogenic stor-
age tank.

SUMMARY
P ROBABLY THE MOST significant conclusion that
can be made from our work and that of others
in low-temperature heat transfer is that much
of the design at these temperatures can generally
be patterned upon design work that has been
successful at normal temperatures. Often, the ex-
ceptions encountered in cryogenic heat transfer
are caused by changes in emphasis or differences
due to properties of the fluids on materials and
the effect of temperature on these properties.
Since transient heat transfer is encountered
in every cool-down of process and storage equip-


ment used in low-temperature service, its under-
standing is extremely important. A common pitfall
is to design these systems by analyzing each part
separately and then failing to bring the inter-
related parts together to establish the complete
design. Regardless of the complexity, it is critical
that these be carefully integrated into the overall
system. A simulation program can be a great aid
in making such an analysis. O


ACKNOWLEDGMENT
The staff and research support over the past
two decades from the University of Colorado and
the Cryogenics Division of the National Bureau
of Standards is gratefully acknowledged. In addi-
tion, appreciation is extended to the Minnesota
Mining and Manufacturing Company and the
ASEE for the Chemical Engineering Division
Lectureship Award bestowed upon the author.


REFERENCES

1. R. F. Barron, Cryogenic Systems, McGraw-Hill Book
Company, New York (1966).
2. A. P. Colburn, Trans. AIChE 29, 174 (1933).
3. E. R. G. Eckert, Heat and Mass Transfer, McGraw-
Hill Book Company, New York (1963).
4. H. Glaser, VDI Zeitschrift, Beihefte Verfahrenstech-
nik 4, 112 (1938).
5. E. J. Davis and M. M. David, IEC Fund. 3, 111 (1964).
6. J. G. Collier, P. M. Lacey, and D. J. Pulling, Trans.
AIChE 42, T127, (1964).
7. E. D. Grimison, Trans. ASME 59, 583 (1937); 60, 381
(1938).
8. J. M. Chenoweth and M. W. Martin, Pet. Refiner 34,
151 (1955).
9. K. W. Cowans, Advances in Cryogenic Engineering,
Vol. 19 (K. D. Timmerhaus, ed.) Plenum Press, New
York (1974), p. 437.
10. P. G. Kroeger, Advances in Cryogenic Engineering,
Vol. 12 (K. D. Timmerhaus, ed.) Plenum Press, New
York (1967) p. 363.
11. R. W. Lockhart and R. C. Martinelli, Chem. Eng.
Progr. 45 (1), 39 (1949).
12. H. Hausen, Wtirmeiibertragung in Gegenstrom,
Gleichstrom und Kreuzstrom, Springer-Verlag, Berlin
(1950).
13. R. McDonald, Ph.D. Dissertation, Bradford Uni-
versity, Bradford, England (1967).
14. M. H. Seeland, M. S. Thesis, University of Colorado,
Boulder, Colorado (1979).
15. R. B. Bird, W. E. Stewart, and E. N. Lightfoot,
Transport Phenomena, J. 'Wiley and Sons, Inc., New
York (1966) p. 314.
16. B. Carnahan, H. A. Luther, and J. 0. Wilkes, Applied
Numerical Methods, John Wiley and Sons, Inc., New
York (1969), p. 429.


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